French investigators have found the “bones” of a toddler who went missing last summer in a tiny Alpine village and are working to determine how he died, a prosecutor said on Sunday.

The discovery is the first breakthrough in the case of two-and-a-half-year-old Emile, who vanished on July 8 last year while staying with his grandparents.

Two neighbours last saw him in the late afternoon walking alone on a street in Le Haut Vernet, at an altitude of 1,200 metres (4,000ft) in the French Alps.

“On Saturday, the police were informed of the discovery of bones near the hamlet of Le Vernet,” prosecutor Jean-Luc Blachon said.

Genetic testing allowed them “to conclude on Sunday that they were the bones of the child Emile,” he added.

The prosecutor did not give a cause of death, but said that forensic investigators were continuing to analyse the bones.

He said that police were carrying out additional searches in the area where the bones were found.

A source close to the case said a walker had spotted the remains.

Emile disappeared a day after he had arrived to stay with his maternal grandparents in their secondary home for the holidays.

The little boy, barely 35in tall, was wearing a yellow T-shirt, white shorts and tiny hiking shoes when he went missing.

A massive search involving dozens of police officers and soldiers, sniffer dogs, a helicopter and drones failed to find the toddler.

A prosecutor said after several days that it was unlikely such a young child would have survived in the summer heat.

After the initial search a criminal investigation into a possible abduction was launched, although the possibilities of an accident or a fall have also remained open.

Police on Thursday returned to the village, cordoning off the area and summoning 17 people including family members, neighbours and witnesses to re-enact the last moments before he went missing to try to solve the mystery.

Drones flew overhead in the drizzle to capture footage of the re-enactment, but there was no news of any discovery after the exercise.

Emile’s mother and father, devout Catholics, were absent on the day of his disappearance.

The boy was officially in the care of his grandfather, Philippe Vedovini.

Mr Vedovini was questioned in a 1990s case into alleged violence and sexual aggression at a private Catholic school.

In late November, a day before Emile would have turned three, his parents published a call for answers in a Christian weekly.

“Tell us where he is,” they wrote.