British police started excavations on a Greek island on Monday, saying they were armed with new leads into the disappearance of a British toddler there 25 years ago.
South Yorkshire Police, who are leading the investigation, said they would focus their attention on two sites on the island of Kos, close to where the child, Ben Needham, was last seen near his family's holiday home on July 24 1991.
Detective Inspector Jon Cousins, the lead investigator, said new information on the case surfaced in May, following a public appeal to Kos residents.
"I have made a decision that there is a very valid and good reason for us to be doing the activity that we are doing here today," he said. Excavations would continue in the coming days, possibly weeks.
"I would not be doing that if I was not optimistic that we are going to find something of significance that hopefully will provide an answer for Ben's family," Cousins said.
He would not comment on British newspaper reports of speculation that the child may have been crushed by a digger in an accident.
Ben was only 21 months old when he disappeared as he played outside a farmhouse that his family was renovating. Despite repeated appeals and hundreds of possible sightings, the boy has never been found and few firm clues have emerged. A previous dig in the area in 2012 was fruitless.
The hunt is one of Britain's longest-running missing-person inquiries.