Police teams searching for missing toddler Ben Needham on the Greek island of Kos have said they are "optimistic" about new excavation work.
Ben, from Sheffield, was 21 months old when he disappeared on 24 July 1991 during a family holiday.
Digging has begun at a new site after a fresh line of inquiry suggested he could have been crushed by a digger.
South Yorkshire Police (SYP) said it continued to keep an "open mind" about what happened to Ben.
The dig is expected to take 10 to 12 days, with the team of 19 expected to find "hundreds" of bones to be analysed.
Det Insp Jon Cousins, from SYP, said: "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."
He added: "I am optimistic about the search taking place."
The new Greek led investigation, being supported by South Yorkshire police, was triggered by a friend of builder Konstantinos Barkas.
It was claimed Mr Barkas may have accidentally killed Ben while clearing land with an excavator close to where the toddler was playing on the day he vanished.
Mr Barkas reportedly died of stomach cancer last year, months before detectives from South Yorkshire Police arrived on the island for a renewed investigation.
His widow Varvara strongly dismissed any suggestions her late husband had killed Ben.
At the scene: Danny Savage, BBC News
In a sun-baked olive grove overlooking the sea, a team of British detectives are carrying out a fingertip search of the dusty soil.
In another corner of the field a JCB digger is scooping up earth, loading it into a Bobcat to carry away.
This is the routine which will play out up a country lane in Kos over the next week or so.
Will the earth here yield any sign of Ben Needham? The search is literally outside the door of the house where he was last seen alive 25 years ago.
This is organised work following up the best lead this enquiry has probably ever had.
If Ben Needham was accidentally run over and buried by a bulldozer working outside at the time, this is where he is most likely to be.
Detectives want to solve this case for Ben's family who are waiting anxiously for news.
Ben Needham's mother and grandparents were renovating a farmhouse in the village of Iraklise when he vanished.
His family and supporters have led a campaign to find him, while his mother and police officers have appeared on Greek television to appeal for information.
Earlier this year, South Yorkshire Police secured funding from the Home Office to send 10 officers to Kos to carry out further investigations.
The disappearance of Ben Needham
- 24 July 1991: Ben Needham vanishes after travelling to Kos with his mother and grandparents.
- September 1991: Ben's family returns to England due to illness, but his mother Kerry Needham continues to campaign for her son to be found.
- June 2003: The Metropolitan Police issue an image of what Ben might look like at age 12-14 years old.
- February 2011: Prime Minister David Cameron responds to Mrs Needham, offering to support South Yorkshire Police and to press the Greek authorities.
- May 2011: BBC airs a programme called "Missing 2011" which includes a segment on Ben.
- September 2011: Greek police on Kos reopen Ben's case.
- October 2012: A police operation focusing on a mound of earth and rubble close to where Ben was last seen finds no trace of him.
- October 2013: Police say a DNA test carried out on a man in Cyprus proves he is not Ben Needham.
- March/April 2015: A DNA test on another man in Greece proves negative.
- January 2015: South Yorkshire Police gets £700,000 from the Home Office to continue the investigation.
- March 2016: The force secures a further £450,000 in funding.
- May 2016: A team of 10 South Yorkshire Police officers visits Kos to carry out house-to-house visits.
- September 2016: Police say two locations on the island will be excavated.