At least four people were killed when an avalanche hit a ski resort in the French Alps near the border with Italy on Monday, officials said.

The avalanche hit the Tignes ski resort in south-eastern France and dragged at least nine skiers who were off-piste. The police said five people were still missing.

The group consisted of a guide and eight skiers who were at an altitude of 2,100 metres (6,885 feet), BBC reported.

“Five people are still buried under a huge mass of snow,” said a rescue official from nearby Albertville.

The avalanche appeared to have been set off by a group of skiers higher up, the ski station said in a statement.

Rescue services deployed two helicopters as well as sniffer dogs to help search for the missing skiers. The incident is the worst in France since the beginning of this year’s ski season.

The avalanche warning level at Tignes on Monday was three out of five, France’s Dauphine Libere reported.

There were 13 previous skiing accidents in the Alps and Pyrenees this winter, killing three people. Last winter, there were 45 accidents, causing 21 deaths.