HERE'S WHAT WE KNOW SO FAR:
Update 11.50pm: A tenth person has been reported missing.
Known as Tony, the 66-year-old is reported to have last been in contact with his family at around 3am while he was inside the building.
Lee Disson, Tony's son, posted an appeal for information on Facebook and said he was "still praying for him".
The appeal read: "If anyone has seen my Dad, Tony Disson could they let us know. My heart goes out to all the people at Grenfell Tower."
He is reported to have lived on the 10th floor and Sky News said his wife Cordelia and three sons have been searching for him in hospitals.
Update 11pm: Residents had raised concerns about exposed gas pipes at Grenfell Tower weeks before the devastating blaze.
The Grenfell Leasehold Association asked for an "independent adjudicator" to examine the installation of the pipes but were refused by management company Kensington and Chelsea Tenant Management Organisation (KCTMO).
Renovations to replace new gas risers at the 24-storey building, which bring in supplies from street level, were carried out earlier this year by National Grid Gas Distribution - rebranded as Cadent at the end of March.
I am deeply saddened by the tragic loss of life at Grenfell Tower. My thoughts are with all those affected and the emergency services.— Theresa May (@theresa_may) June 14, 2017
In a statement on Wednesday, Cadent said pipes in the stairwells had been boxed in using fire-proof material that could withstand flames for two hours, but that work was still being done to box in pipes running along floors.
A spokeswoman for the company said: "All our gas work was carried out to regulatory standards."
The GLA repeatedly emailed the KCTMO in March over worries that one riser was installed in the single stairwell - the only emergency exit - and could have been vulnerable to vandalism.
Association representatives also raised concerns about health and safety issues around exposed pipes.
In a letter to representatives on March 28, Sacha Jevans, executive director of operations at KCTMO, said the organisation takes its health and safety responsibilities "very seriously".
Scene at a mosque near Grenfell Tower. More and more supplies arriving. Food for everyone and beds laid out. Incredible support. pic.twitter.com/vZSB9WIXHN— Joe Tidy (@joetidy) June 14, 2017
She wrote: "We do not see that it is necessary to instruct or fund an 'independent adjudicator' at this time."
Ms Jevans also told them National Grid had found the stairwell was the only option for the riser pipe, and the fire safety consultant had "not raised any specific concerns with regards to its location providing it is located within a suitably fire-rated enclosure".
Update 9.16pm: Dozens of people have gathered for a vigil in the shadow of the Grenfell Tower.
Many were moved to tears after a moment of silent contemplation outside the Notting Hill Methodist Church in west London.
The Rev Mike Long invited those present to light candles to place on the steps of the church on Wednesday evening.
He then played Amazing Grace on his flute as members of the crowd sang along.
He 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."
He added: "Let light triumph over all that is rotten, that is desperate and that defies our understanding."
Meanwhile, four more people have been reported missing.
Believed to be a mother of two small children, Rania Ibrham, 30, uploaded a harrowing Facebook Live video as she appeared to be stuck at the top of the tower block, and has not been heard from by friends since.
In the footage, she can be seen seeking help in the smoke-covered corridor of the block before going back into her home and looking down on the street below from her balcony.
Friend Rahmana Rashid posted a picture of her and two young girls on Facebook saying: "Rania Ibrham my friend is missing from the grenfill tower, if you have seen her or have any news on her pls contact me."
Another friend, named only as Maseen, told the MailOnline: "My friend, Ranya Ibrahim, lives on the top floor with her two children who are just three and five years old."
"I received a Snapchat video from Ranya at 3am just after the fire started and I haven't heard from her since," she added.
"She lives on the top floor and her husband was not home because he is on holiday."
Noha Baghdady shared a picture of her brother Hesham Rahman, 57, across a number of platforms, saying he lived on the 20th floor of the tower block and had not heard any news since the fire broke out.
She said her nephews were "currently searching hospitals" and added: "I'm feeling so helpless all we can do is pray he is safe and well."
According to Sky News, Mr Rahman's last contact with his family was at around 3am when he told them he could smell smoke.
It was also reported that Mr Rahman has diabetes, making it difficult for him to walk down stairs.
Londoners unite in the face of tragedy, donating food, hotel rooms and even their homes to victims of the Grenfell fire. pic.twitter.com/iURRCAzcnQ— Channel 4 News (@Channel4News) June 14, 2017
Stevan Racz shared a post seeking information about his uncle Dennis Murphy, whom he said had called while trapped on the 14th floor of the building.
"We haven't heard anything since. Can anyone with any information contact me please," he said.
One commenter on another post seeking Mr Murphy wrote: "I've been around asking everyone, going to the centres, no one's seen him."
A friend of missing Mohamed Neda, Ariana Neumann Rodger, posted on Facebook that "his family are severely injured and in hospital and desperate to find out where he is".
Zia Popal, who described Mr Neda as his uncle, also posted on the social network and said: "He was on the top floor of the building trying to help (people) and went missing since.
"If anyone has links with emergency services please take a look at his photos and pass them on just in case anyone has spotted him.
"We have already been to all (the five) major hospitals but they do not have him registered."
Earlier: Twelve people have died and more are feared dead after a huge fire destroyed a tower block in west London.
Flames tore through the 24-storey Grenfell Tower in north Kensington overnight, leaving people trapped on upper floors - some holding babies out of windows and others jumping from their flats.
Some bodies have been removed from the smouldering remains of the building, which contains 120 flats thought to be home to between 400 and 600 people.
Commander Stuart Cundy of the Metropolitan Police said: "Sadly I can confirm that there are now 12 people that have died that we know of.
"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."
Fire crews are continuing to tackle "pockets of fire" in the building with many people still unaccounted for.
Steve Apter, director of safety and assurance at London Fire Brigade, said: "I can confirm I have had firefighters manage to get through particularly arduous conditions up to the top floor."
London Fire Brigade said it had rescued 65 people from the building.
Mr Cundy added: "Whilst we may have accessed every floor that is not the same as a full search of the whole building, and as I said while we currently sadly have 12 fatalities, I do believe that figure will rise and sadly I don't anticipate that there will be further survivors."
NHS England said 74 patients were treated in six hospitals across London. Thirty four patients remain in hospital including 1 8 who are in critical care.
There have been calls for a major investigation amid questions about how the fire spread so rapidly through the block.
London Fire Commissioner Dany Cotton earlier told reporters: "This is an unprecedented incident. In my 29 years of being a firefighter, I have never ever seen anything of this scale."
Prime Minister Theresa May was said to be "deeply saddened by the tragic loss of life" and newly appointed police and fire minister Nick Hurd will chair a meeting of the Civil Contingencies Secretariat to co-ordinate the response.
Labour leader Jeremy Corbyn said "searching questions" need to be asked about what happened, suggesting spending cuts could have contributed to the deadly fire.
He said: "If you deny local authorities the funding they need, then there is a price that's paid."
Built in 1974, Grenfell Tower was recently refurbished at a cost of £8.6 million, with work completed in May last year.
Rydon, the firm that carried it out, said its work "met all required building control, fire regulation, and health and safety standards".
London Mayor Sadiq Khan said: "There will be a great many questions over the coming days as to the cause of this tragedy and I want to reassure Londoners that we will get all the answers."
Nick Paget-Brown, leader of Kensington and Chelsea Borough, said: "Clearly, looking further ahead there needs to be a full investigation into the cause of this fire, why it started and why it appears to have spread so rapidly."
London Fire Brigade said the cause of the fire is still being investigated, but several residents reported one man had said it started in his faulty fridge.
Witnesses said the fire spread rapidly and traumatic accounts have emerged of the desperate attempts made by residents to flee the flames.
Samira Lamrani said she saw a woman try to save a baby by dropping it from a window ''on the ninth or 10th floor'' to waiting members of the public below.
Tiago Etienne, 17, heard people pleading for help as the building was engulfed in flames.
She said: "I saw children being thrown out of the building from as high as about the 15th floor. They were young - aged probably between four and eight. I saw three thrown out.
"I think they were being thrown out for the firefighters or police to catch, but I couldn't see from where I was who was at the bottom and what they were catching them in."
Local councillor Judith Blakeman, who lives opposite the tower, rushed outside when she heard about the blaze at 5am.
She said: "Neighbours had been watching it all night, they said the cladding went up like a nightdress by a fire - it just went whoosh."
Residents who escaped complained there had been no fire alarm, with many relying on neighbours to wake them as the blaze spread, and said official advice in the event of a fire had been to stay inside.
Michael Paramasivan, who was in his seventh floor flat with girlfriend Hannah West, 23, and her daughter Thea, five, said: "If we'd listened to them and stayed in the flat we'd have perished."
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.
Mr Paramasivan, 37, told the Press Association: "There were explosions everywhere you looked, lots of bangs, blue gas coming out everywhere you looked.
"About 12 floors up I saw three children waving from a window and then there was just an explosion and they disappeared.
"They were three kids, they were banging on the windows, you could see their silhouettes and then bang, it just went up."
Flowers had been placed beside the taped-off police cordon, which was being guarded by uniformed officers.
Attached to a mixed bouquet was a card with the message: "Love and prayers to the families and victims. Justice has to be done. People before money. RIP."