Police teams searching for missing toddler Ben Needham on the Greek island of Kos say they are "optimistic" a new excavation will provide answers, a quarter of a century after the British boy was last seen alive.
Digging began after a fresh line of inquiry suggested 21-month-old Ben may have been crushed to death by a digger near a farmhouse his grandparents were renovating in July 1991.
Senior investigating officer Detective Inspector Jon Cousins, from South Yorkshire Police, said the 19-strong team expected to find "hundreds" of bones, all of which will be analysed in laboratories once they are recovered.
But he also refused to rule out that Ben may still be alive.
He said: "I am continuously keeping an open mind - and still do - as to what happened to Ben in 1991.
"There are still some other live lines of inquiry of what might have happened to Ben.
"All of this has resulted in a lot of myth and legend that has gathered over 25 years as to what has happened to Ben. It has allowed us to pare back and find out the truth and fact. That is why we're here today."
He added: "There are many lines of inquiry. I am keeping an open mind, but what I know at the moment with all the information we have, I've made the decision that it is necessary to do the work that we are going to be doing over the next week or so."
Asked if he expected to find answers, Mr Cousins said: "I am optimistic about the search taking place."
Konstantinos Barkas, also known as Dino, was clearing land with an excavator close to where Ben was playing on the day he vanished and may be responsible for his death, a friend of the builder reportedly told police following a TV appeal in May.
The driver reportedly died of stomach cancer last year, months before detectives from South Yorkshire Police arrived on the island for a renewed investigation.
Mr Cousins said: "Based on what we found out in 2012 when a search was done nearby, we will be finding many hundreds of bones, each of which will have to be carefully looked at.
"Work will continue tirelessly once work has been assessed."
Forensic teams could be seen walking slowly in banks of around eight as the site - which continues to be farmed by a local family - was sectioned off into grids.
Investigators have already told Ben's mother Kerry Needham to "prepare for the worst" ahead of excavation work beginning on the island.
Speaking to the Press Association from the site, senior investigating officer Mr Cousins said he had a "private" chat with Ms Needham, who is not in Kos.
He said: "I personally spoke to Kerry this morning and explained what I would be doing today.
"I had a private conversation with her around how she was feeling, and also explained the emotion that all of the team are feeling at this time.
"It is an event which quite clearly is not something to be excited about, given the circumstances, but we are optimistic about the work we are going to be doing."
He also said police had been reminded about their conduct after newspaper reports earlier this year which identified members of the investigation team in Kos on an alleged "eight-hour" drinking session.
Mr Cousins said: "Clearly each member of the team and everybody working with us has the right to a private life.
"I've briefed everybody. They understand there is a job to do.
"We will abide by the codes of conduct not only expected of the senior leadership group of South Yorkshire Police, but UK police as a whole. We will always be seen to be acting professionally and with integrity.
"We're here for the reasons of finding what happened to Ben. That's mine and the team's main objective."
Asked whether that meant police would be seen out drinking in Kos, Mr Cousins said: "Everybody's been briefed as to what's expected of the behaviour throughout this time they are going to be here and they are fully aware of what they need to be doing."
It came as Ben's mother said the notion her son was dead never entered her "worst nightmares" until a mystery tip-off to police this year.
Ms Needham, from Sheffield, told the Daily Mirror: "Not even in my worst nightmares has Ben ever been dead ... until now. I've been waking up and finding my pillow wet with tears.
"This witness told police we deserve the truth - but we deserved the truth 25 years ago. I feel like he's only come forward because Dino is now dead.
"How can you hold on to such a secret as serious as that and for all those years?"
She added she was "angry" when police told her about the tip-off and she now lives in fear that each day will bring the "worst news possible".
A variety of theories on his fate and reported sightings have arisen since his disappearance and Ms Needham had been holding out hope that she would one day be reunited with her son.
Mr Barkas's widow Varvara strongly dismissed any suggestions her late husband had killed Ben in an accident.
South Yorkshire Police has confirmed that its team, led by Detective Superintendent Matt Fenwick, will begin searching a specific site on Kos, starting on Monday. But it warned progress could be painstaking, with the first dig expected to last up to 12 days.
Detectives are said to have carried out initial inquiries at the site, with experts testing soil and surveying the area with drones.