The avalanche at the Deux Alpes resort left two pupils dead as well as a Ukrainian man who was not with the group.
The focus of the investigation by French police has been on the actions and the character of one of the teachers who was in charge of the pupils from a school in Lyon.
On Thursday the 47-year-old teacher, who was knocked unconscious by the snow-slide, was formally questioned on suspicion of “multiple manslaughter”.
The following day reports emerged in the French press that the teacher had spent time receiving treatment in a psychiatric hospital during November.
According to Le Parisien newspaper the teacher was still receiving treatment, including anti-depressant medication for the same health problems that forced him into the psychiatric hospital.
Other reports in the French media claimed he lacked authoriy.
If the reports are confirmed, then more questions will be asked about the suitability of the teacher to be left in charge of a group of pupils on a ski trip.
There were also reports on Friday that the teacher had led pupils down the same closed piste the day before the tragedy struck.
Since news of Wednesday's tragedy broke questions have been raised about why the pupils were skiing on a black level slope – the most difficult level – when it was not open to the public.
But despite being questioned for possible multiple manslaughter the prosecutor warned against passing judgement on the teacher.
“I remind you that this teacher benefits from the presumption of innocence,” he said. "This type of disaster is a result of chain of events that needs to be defined.
“It needs to be remembered that skiing off-piste is not a crime and it's not forbidden,” he added.