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 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.
Disappearance of Ben Needham
• 24 July 1991 - Ben disappears
21-month-old Ben vanishes while in the care of his grandparents Eddie and Christine Needham on the Greek island of Kos.
• 25 July 1991 - Kos Town searched
The Needhams join police in searching for Ben on the hillside above Kos Town, but find no trace.
• September 1991- Needhams return home
Nearly two months after Ben's disappearance, the Needhams return home to Sheffield having run out of money to sustain the search.
• 1993 - Ben's mother returns to Kos
Ben's mother Kerry returns to Kos for an update on the investigation but no information is forthcoming from the Greek police.
• 1995 - Blonde boy found
A blonde boy, aged around six years old, is found to be living with a Gypsy family in a camp located in Salonika, Greece.
The child claims he was given to the Gypsies after being abandoned by his biological parents but there is no evidence to suggest this is Ben Needham.
• 1996 - Prison lead
Ben's grandparents Christine and Eddie meet with a prisoner in the Greek city of Larissa who claims to know someone holding Ben. This ultimately fails to produce a positive sighting.
• July 2011 - Cold case review launched
A cold case review is launched by South Yorkshire Police and officers are sent from Athens to Kos to give new impetus to the investigation.
• November 2011- DNA ruling
The High Court rules that DNA obtained from a Guthrie heel-prick test when Ben was born can be used by police.
• May 2012 - Police consider excavation
Police consider excavating land in Kos to look for Ben's body after a digger driver claims he was excavating in the area at the time of the disappearance.
• October 2013 - Video lead
Greek police are handed a video of a man in Cyprus with a "striking resemblance" to a computer-generated image of how Ben would look now.
However, a DNA test proves that the man is not Ben.
• January 2015 - Extra funding
A Home Office announcement of extra funding for the Ben Needham investigation comes just weeks after his mother threatened to sue the Home Secretary.
• May 2015 - Greek TV appeal
Kerry Needham travels to Athens to make a direct TV appeal on Greek missing persons show Light at the End of the Tunnel.
• July 2015 - Police pursue "several lines of enquiry"
South Yorkshire Police confirms that officers will continue to visit Kos over the coming months, to pursue "several lines of inquiry".
• September 2016 - New excavation
Police plan a new search for Ben's body after a new witness is said to have claimed the toddler 'could have been crushed by a digger' in a fatal accident.