Two teenagers and a Ukrainian tourist died after being caught up in an avalanche in the Deux Alps area
A French teacher - who brought a group of students onto the Alps yesterday when an avalanche hit - may face criminal charges.
Three people died and several others were badly injured after the avalanche hit a group of school pupils skiing on the piste, which had been closed to the public all season.
"A judicial inquiry will say why the teacher who was himself injured took (the group) onto a piste which was not open," French Minister for Youth and Sports Patrick Kanner said.
"How can you think of taking children, following periods of heavy snowfall, onto a piste which was closed?"
Two of the dead were teenagers aged 14 and 16, while a Ukrainian skier who was not with the group also lost their life.
Around 19 secondary school pupils were also caught up in the avalanche.
Three pupils suffered cardiac arrest while the teacher was also seriously injured, said a government official.
The casualties have been taken to hospital in Grenoble.
All other students from the group had been accounted for and were safe, the interior ministry said.
Rescue teams also searched for other skiers who might have been buried in the snow.
The disaster happened on a closed ski run around 4pm local time (3pm Irish time) in the Les Deux Alpes resort.
Commander Bertrand Host told BFM television there had been an avalanche warning in the area before the tragedy.
The level of risk had been put at three out of a maximum five after several centimetres of snow fell on Wednesday afternoon and made conditions unstable.
Around 60 people were taking part in the search, including 30 mountain rescue workers.
Two police helicopters and an emergency rescue helicopter were also on the scene along with search dogs.
One rescue worker reportedly said there was a very thick layer of snow after the avalanche, making it even more difficult to find the missing.
Conditions for skiing and hiking have been difficult because of heavy snowfall in recent days.
The group of pupils and their teacher was from the St Exupery college in Lyon and was on a week's holiday in the area.
Since the start of January, four people had lost their lives in avalanches in the French Alps.
They included two Lithuanian mountaineers, as well as a Spanish and Czech skier.