Latest: A criminal investigation has been launched in the wake of the fatal fire.
It followed calls for those involved in the building's recent renovation - which many claim posed a major safety risk - to face prosecution.
Update 7.10pm: A criminal investigation has been launched in the wake of the fatal fire.
It followed calls for those involved in the building's recent renovation - which many claim posed a major safety risk - to face prosecution.
"We as the police have started an investigation, I mentioned when I was down at the scene this morning that one of our very senior investigating officers is leading that for us," the commander said.
"We as the police, we investigate criminal offences - I am not sitting here and saying there are criminal offences that have been committed, that's why you do an investigation, to establish it.
"This will need to be a lot of work between us and other investigating agencies to establish what has happened and why and that is going to take a considerable period of time."
Detective Chief Inspector Matt Bonner from the homicide and major crime command has been appointed to lead the investigation.
The fire was initially extinguished shortly after 1am - a full 24 hours after the first alarms were raised - paving the way for tentative searches in Grenfell's worst-affected areas.
Pls RT to thank all of the emergency services who acted so professionally and bravely at Grenfell Tower - you are all heroes pic.twitter.com/fGPH13K7h3— NHS Million (@NHSMillion) June 15, 2017
But the blaze flared up again on Thursday afternoon, forcing search teams to scale back their efforts.
Detective Superintendent Fiona McCormack said the lingering threat had also hampered the process of recovering bodies.
"At this moment in time, the fire is still ongoing, so it is not safe to take people out of the tower," she told reporters.
The police's casualty bureau was said to have received 5,000 calls during the chaotic first day of the investigation.
Around 400 people were reported missing, but Mr Cundy downplayed the figure, saying it added up to more people than actually lived in the block. One person was reported missing 46 times, he added.
Update 5.50pm: The Mayor of London has called for an interim report into the Grenfell Tower fire to be published this summer and for the public inquiry to examine whether the block was refurbished safely.
Sadiq Khan said there were "questions that demand answers", adding: "We can't afford to wait many years for those answers."
It comes after British Prime Minister Theresa May ordered a full public inquiry into the disaster to establish what had happened.
Speaking near the scene of the blaze in west London, Mr Khan said: "One of the things the public inquiry will look into is the refurbishment of the tower blocks and whether the tower block was refurbished in a safe way.
"There are obvious questions about value for money and other questions that will be raised and other questions that demand answers.
"We can't afford to wait many years for those answers. Which is why I am today calling for an interim report to be published this summer."
Update 5.10pm: Police fear they may not be able to identify everybody killed in the Grenfell Tower disaster.
Six bodies have so far been recovered from the gutted 24-storey tower, while 11 have been located inside but cannot be removed.
The death toll from the blaze is 17, but that figure is expected rise significantly.
Metropolitan Police Commander Stuart Cundy said: "It may be - and I just don't know - it may be that ultimately some victims remain unidentified.
"I won't know that until we've gone through the full recovery from Grenfell Tower and we know exactly what we've got and I anticipate that is going to take a considerable period of time.
"Not just the immediate recovery of the bodies we have found but the full search of that whole building we could be talking weeks we could be talking months - it is a very long process.
"There is a risk that sadly we may not be able to identify everybody."
His comments came as Prime Minister Theresa May ordered a full public inquiry into the disaster.
Meanwhile, more than 60 tonnes of donations for victims of the Grenfell Tower fire have been collected by a local mosque.
Scores of volunteers gathered at nearby Al Manaar mosque to help with the relief effort.
They formed lines to sort boxes of clothing, toiletries, food and baby supplies donated by the community.
There have been so many donations that the group has taken over a local warehouse to store all the supplies.
Kamran Siddique of Muslim Aid, which is working with the mosque, said: "We have got a couple of hundred volunteers from all over the country from diverse backgrounds.
"People have been here since early on Tuesday and are still here now.
"A lot of us are fasting as well - it feels like sandpaper in my mouth.
"We've got over 60 tonnes of clothing, toiletries, bedding, food, medicine - we have now come to the point where we can't take any other donations.
"Our plan is to get it sorted, boxed and inventoried so that we can share it with other organisations.
"Residents of Grenfell are all over the place so we will do a needs assessment."
The only thing the group needs now is more empty boxes to store all the donations in, he added.
"There are a lot of Muslims in the area and we've all come together with others from all different backgrounds to help," Mr Siddique added.
Update 2.45pm: One of the first victims of the Grenfell Tower fire has been named as 23-year-old Syrian refugee Mohammed Alhajali.
Co-founder of the Syria Solidarity Campaign Abdulaziz Almashi confirmed the news, saying he had met Mr Alhajali whilst working for the organisation which promotes freedom, peace and democracy in Syria.
Mr Almashi said: "He (Mr Alhajali) was kind, charitable and full of passion for his family. I can't believe he's not here."
Mr Alhajali studied civil engineering at the University of West London. He wanted to study the subject so that he could one day return to Syria and help the country, said Mr Almashi.
His brother Omar Alhajali was also caught up in the blaze but was found in hospital in a stable condition.
Update 1.40pm: British Prime Minister Theresa May has ordered a full public inquiry into the Grenfell Tower fire disaster.
After visiting emergency teams at the scene of the blaze in west London, Mrs May said a proper public investigation was needed to establish what happened.
Speaking at 10 Downing Street shortly after her return from the site, she said: "We need to ensure that this terrible tragedy is properly investigated."
"We need to know what happened, we need to know an explanation.
"We owe that to the families, to the people who have lost loved ones and the homes in which they lived.”
Mrs May's announcement came just before a demand by mayor of London Sadiq Khan that an inquiry be held.
He said the "full scale of the tragedy is becoming clear and there are pressing questions, which demand urgent answers".
"That is why I am demanding a full, independent public inquiry into the fire at Grenfell Tower. In light of concerns about the safety of other tower blocks that have been similarly refurbished, the inquiry needs to produce an interim report by the end of this summer at the latest."
Mrs May added: "When I went to the scene and spoke to the emergency services, they told me that the way this fire had spread and took hold of the building was rapid, it was ferocious, it was unexpected.
"So it is right that, in addition to the immediate fire report that will be produced and any potential police investigation, that we do have a full public inquiry to get to the bottom of this.
"People deserve answers. The inquiry will give them."
Update - 11.37am: Specialist urban search and rescue teams are being brought in to make the 24-storey tower block safe in north Kensington to allow firefighters and the police to carry out investigations.
Search dogs will also be used to help locate the missing in the wreckage.
London Fire Commissioner Dany Cotton said: "This will be a detailed fingertip search.
"Obviously this will be a very slow and painstaking process."
The flats were home to between 400 and 600 people, community leaders said.
More than £1m has been raised to help those affected by the fire, while volunteers and charities helped feed and shelter people who could not return to their homes overnight.
A wall of condolence was put up near the scene, with photographs showing dozens of messages left for loved ones.
British Prime Minister Theresa May has visited the scene this morning, speaking with firefighters and police officers inside the vast cordoned-off area around the fire site.
She has promised a "proper investigation" after the building went up in flames amid growing concerns about how the blaze could have spread so rapidly.
She was whisked away by car shortly after 10am without speaking to reporters.
Update - 11.01am: 17 people have died in the Grenfell Tower fire but the death toll is still expected to rise, Commander Stuart Cundy of the Metropolitan Police said.
Commander Cundy also said a senior detective, DCI Matt Bonner, has been appointed to lead the investigation into the Grenfell Tower fire.
London Fire Brigade (LFB) said firefighters have been able to search almost all of the building more than 30 hours after the fire broke out, although flare-ups are still happening, with flames seen throughout last night.
However, they have not be able to reach beyond the 20th floor of the 24-storey block as the structure is too unstable.
London Fire Commissioner Dany Cotton, said: "Sadly we do anticipate the death toll will rise - we haven't done our searches of the top floors yet."
The firefighters could face future psychological issues, Ms Cotton has warned.
London Fire Brigade said more than 200 firefighters and 40 fire engines attended the scene after the blaze ripped through the 24-storey block in west London, from the second floor upwards.
She said the firefighters had been particularly affected by the desperation of one family who threw a baby from a window in a bid to save it.
She told Sky News: "For my crews who were on the ground who witnessed it happening it was truly horrible and shocking.
"I spoke to one of my officers who was very near when someone came out of the window, he was in tears. He is a professional fire officer.
"We like to think of ourselves as roughty-tufty and as heroes but they have feelings. People were absolutely devastated by yesterday's events."
Update - 10.09am: A total of 37 people are still being treated in hospital, with 17 in critical care, NHS England said in a statement.
Update - 9.33am: The London Fire Brigade (LFB) said a ruptured gas main in the block had to be isolated before fire crews were able to put the blaze out and bring it under control by 1.14am.
A 40 metre aerial appliance was brought in from Surrey Fire and Rescue Service to help with this.
Ms Cotton said the number of people who are unaccounted for is still unknown as some may have got out by themselves or gone into other flats.
The cause of the fire is still being investigated.
A large number of material has been taken away for sampling in detailed searches of the flats as evidence is collected along with identification of the people who live in the flats.
She said "in quite a short period of time" investigators will try to pinpoint the cause of the fire.
Firefighters who worked in intense heat and under falling debris have suffered nine minor injuries, ranging from burns, smoke inhalation and heat exhaustion but the potential psychological damage to them could be a future concern.
British Prime Minister Theresa May is expected to visit the scene of the tragedy later on Thursday to speak with emergency services and ensure that they have the resources they need to deal with the situation.
Update - 9.13am: There are still "unknown numbers" of bodies in Grenfell Tower following the devastating inferno, London Fire Commissioner Dany Cotton has said.
At least 12 people died after the huge fire destroyed the block in north Kensington, west London, where flames could still be seen burning more than a day on from the disaster.
The commissioner told Sky News: "Tragically now we are not expecting to find anyone else alive. The severity and the heat of the fire would mean it is an absolute miracle for anyone to be left alive."
She said there are still "unknown numbers" of people in the building.
More than £1 million has been raised to help those affected as fire tore through the 24-storey building while volunteers and charities helped feed and shelter people who could not return to their homes overnight.
Ms Cotton said the upper floors of the building are still to be searched.
"Sadly we do anticipate the death toll will rise - we haven't done our searches of the top floors yet," she told reporters at the scene.
Earlier: The death toll from the devastating tower block fire in west London is expected to rise as investigators trawl through the wreckage in the search for other victims.
At least 12 people have died after the huge fire destroyed Grenfell Tower in north Kensington, where flames could still be seen burning more than a day on from the disaster.
More than £1 million has been raised to help those affected as fire tore through the 24-storey building while volunteers and charities helped with feed and shelter people who could not return to their homes overnight.
A wall of condolence was put up near the scene with photographs showing dozens of messages left for loved ones.
British Prime Minister Theresa May has promised a "proper investigation" after the building went up in flames early on Wednesday morning amid growing concerns about how the fire could have spread so rapidly.
Speaking in Downing Street, Mrs May said: "When it's possible to identify the cause of this fire, then of course there will be proper investigation and if there are any lessons to be learnt they will be, and action will be taken."
Residents' groups have claimed they voiced concerns about the safety of the building, which had been recently refurbished, while those who escaped complained their fire alarms had not been set off by the blaze.
One focus for the investigation will be the building's cladding, which TV architect George Clarke said may have accelerated the blaze.
Mr Clarke, who lives locally and appears on Channel 4's Amazing Spaces, told BBC's Newsnight: " I saw those cladding panels, the cladding on the outside and the insulation was just peeling off, like you'd peel a banana.
"It was fully on fire. I could see the flames behind - there's a new cladding system put on the outsides that looks like a new skin, there's an air gap an insulation behind that, to me that looks like a fantastic chimney for the fire to rage around."
Grenfell Tower, which built in 1974, was recently refurbished at a cost of £8.6 million, with work completed in May last year.
Kensington and Chelsea Council admitted it had received complaints over the works, after a residents' action group said its warnings about safety had fallen on "deaf ears".
A blog post from Grenfell Action Group in November said "only a catastrophic event" would expose the concerns residents had.
The group said there was one entry and exit to the tower during improvement works and it had issues with evacuation procedures.
Concerns had also been raised about exposed gas pipes weeks before the devastating blaze.
Rydon, the firm that carried out the refurbishment work, said the project "met all required building regulations", in its latest statement following the fire.
But a line stating that the project had met all "fire regulation and health and safety standards", which was included in an earlier release, had disappeared.
When questioned about residents' worries about fire safety at the block, the council's deputy leader Rock Feilding-Mellen told the BBC: "My understanding is that their concerns were looked at and officers and the TMO (tenant management organisation) made inquiries and felt we had done what was necessary."
Meanwhile, work is continuing to tackle "pockets of fire" in the block, with several residents reporting one man had said it started in his faulty fridge.
Many people are still unaccounted for with firefighters saying the operation now in the "recovery phase".
Commander Stuart Cundy of the Metropolitan Police said: "This is going to be a long and complex recovery operation and I do anticipate that the number of fatalities will sadly increase beyond those 12."
Witnesses described hearing screams for help from people trapped on the upper floors of the block as flames engulfed the building, which contains 120 flats thought to be home to between 400 and 600 people.
Children and a baby were seen being thrown out of the windows to be caught by emergency workers and members of the public below.
London Fire Brigade said it had rescued 65 people as flames engulfed the block, and had managed to reach all 24 floors, though a full search of the building has not been completed.
NHS England said 74 patients were treated in six hospitals across London. Thirty-four remain in hospital including 18 who are in critical care.
On Wednesday evening, dozens of people gathered for a vigil in the shadow of the tower as the sun began to set.
Many were moved to tears after pausing for moment of silent contemplation outside the Notting Hill Methodist Church in west London.
The Rev. Mike Long said: "There are times when all the words we can say are not adequate and sometimes words fail us because no words can do justice to how we feel, or what we have seen or what has happened. Today is one of those days.
"What we can simply do is look to all that we have seen today which is good, which is fabulous - people getting together."
Emergency accommodation had been provided to 44 households affected by the fire, with families with young children, elderly residents and those who are vulnerable given "immediate priority", the local council said.
People unable to return to their homes were offered a place to stay at Westway Sports Centre in Crowthorne Road, north Kensington.
Labour leader Jeremy Corbyn said "searching questions" need to be asked about what happened, suggesting spending cuts could have contributed to the deadly fire, while general secretary of the Fire Brigades Union Matt Wrack said: "The truth is this should not be happening in the UK, one of the wealthiest countries in the world."