PARIS (AP) — A Paris prosecutor opened a preliminary judicial investigation on Friday for unvoluntary manslaughter aggravated by breach of safety rules, after a fire left 11 dead at a vacation home housing adults with disabilities in eastern France.

Wednesday's fire killed 10 adults with slight intellectual disabilities and one person accompanying them.

The judicial investigation will seek to determine the cause of the blaze, according to a statement from the prosecutor's office.

It comes after the discovery that required safety standards weren’t met at the private vacation house in the Alsacian town of Wintzenheim.

“The first investigations led to question the legal and material safety conditions of the building,” which was housing 28 people, the statement said.

A prosecutor in Paris has taken over the case because of the high number of victims and the scale of the investigation, it said. The case was previously being supervised by the deputy prosecutor of Colmar, in eastern France.

Vacationers were sleeping when the fire broke out early on Wednesday.

Only five of those who were staying on the upper floor of the house survived, including three vacationers and two staff accompanying them. They were all able to get out of the hospital by the end of the day on Wednesday, the statement said.

Twelve others who were staying on the ground floor were able to evacuate.

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.