A South Yorkshire police officer (R) and members of the Greek rescue service (in red uniforms) investigate the ground while excavating a site for Ben Needham, a 21 month old British toddler who went missing in 1991, on the island of Kos, Greece, September 28, 2016. REUTERS/Vassilis Triandafyllou/Files

ATHENS (Reuters) - A British toddler who disappeared on a Greek island 25 years ago may have died as the result of an accident on the day he went missing, British investigators said on Monday.

In a dramatic turn to what is one of Britain's longest-running missing person inquiries, British police wrapped up a search on the island of Kos saying they had recovered an item during a dig thought to belong to the child, Ben Needham.

Ben was 21-months-old when he disappeared while playing outside a farmhouse his family was renovating as a holiday home in 1991.

"It is my professional belief that Ben Needham died as a result of an accident near to the farmhouse here ... where he was last seen playing," Detective Inspector Jon Cousins of South Yorkshire police told journalists.

It is the first time British police have been so explicit on what they think may have happened to the child on the day he disappeared.

Despite repeated appeals and hundreds of possible sightings, few firm clues have emerged previously on the toddler's disappearance.

Fresh information surfaced after another public appeal in May. It suggested the possibility the child may have died after being hit by a heavy vehicle, leading police to focus their search on two specific locations.

It is unclear why this information never surfaced before.

There was activity in the area at the time of Ben's disappearance, with the use of heavy machinery and a large digger.

British police and forensic experts had searched two locations, one in the immediate vicinity of the farmhouse, and a second where it was thought earth was transferred and dumped.

Cousins said an "item" found at one of the sites police were searching two days ago was thought to be in Ben's possession around the time he went missing. He said that was their initial understanding, and that item had been shown to the child's family.

"Ben’s family have been provided with a full and thorough account of the events which we know to have taken place and also the speculations that we have been able to discount," Cousins said.

(Reporting by Michele Kambas; Editing by Alison Williams)