Required safety standards were not met at a holiday home for adults with disabilities where a heavy fire left 11 dead in eastern France, a deputy prosecutor has said.

A day earlier, the fire killed 10 adults with slight intellectual disabilities and one person accompanying them.

Nathalie Kielwasser, the deputy prosecutor of Colmar, said the first phase of the investigation shows that a mandatory safety inspection for such private accommodation facility had not been done.

Firefighters who took part in the rescue operation speaking with French prime minister Elisabeth Borne
Firefighters who took part in the rescue operation spoke to French prime minister Elisabeth Borne on Wednesday (Sebastien Bozon, Pool Photo via AP)

Speaking on French news broadcaster BFM TV, she said the fire started from the upper floor, but its cause has not been determined.

The building in the Alsacian town of Wintzenheim was equipped to receive 28 people, including 12 on the ground floor and 16 on the upper floor, she added. It was equipped with smoke detectors, she added.

The large holiday home was rented to groups of people by a private owner, who was not identified. It was not specifically dedicated to people with disabilities.

The disabled adults were on a holiday sponsored by two specialised associations. They were staying in the building where the ground floor was made of stone and the upper part was constructed of wood with heavy timbers in the traditional style of the region – a factor that might partly explain why the fire spread so quickly.

The local administration of the Haut-Rhin region said the fire broke out at 6.30am on Wednesday.

Firefighters tackling the blaze at a vacation home in the town of Wintzenheim
11 people died in the fire (TNN/dpa via AP)

Only five of those who were sleeping on the upper floor managed to escape, authorities said. All 12 people who were staying on the ground floor were able to evacuate.

No details about the victims were provided. Investigators were working on identifying the bodies via DNA testing, Ms Kielwasser said.

Fadila Khattabi, minister for disabled people, went to the site on Thursday and met with families of victims who were “in a state of shock,” she said.

“We must tell all the truth to the families,” she said.

It was the deadliest fire in France since an August 2016 blaze that killed 14 people in a basement nightclub in the western city of Rouen.