Three skiers including two Britons have died after being caught in an avalanche in the French Alpine resort of Val d’Isère.

Both were part of a group of four people skiing off-piste under the supervision of an instructor when they were engulfed in the snow slide, according to Cédric Bonnevie, Val d’Isère’s piste director.

“The avalanche hurtled down a 400 metre slope and ended in a stream,” he said.

The third victim was a Frenchman skiing on his own above the Britons. A manslaughter inquiry has been launched, according to Benoît Bachelet, the state prosecutor in Albertville.

He said the cause of the avalanche was unknown, although Ici, the local branch of French state radio, said it might have been triggered by the solo French skier.

Bonnevie said all the victims had avalanche safety equipment including transceivers. Two were found rapidly although the search for the third took longer, with dogs brought in to help. The body was located in the stream at the bottom of the slope where the waterlogged transceiver had stopped working, according to Bonnevie. The victims have not been identified.

A snowy ski resort town nestled between large snow-covered mountains.

Val d’Isère, in the French Alps

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Bachelet said a third Briton was also caught in the avalanche but escaped with minor injuries. He is thought to have dug himself out of the snow before being transported to hospital. The instructor, who was unhurt, underwent alcohol and drug tests which were negative, the prosecutor said.

The incident came a day after many French ski resorts had closed their pistes because the avalanche risk was classified as 5/5 — the first time in 17 years that it had reached the maximum level.

Slopes reopened on Friday although the avalanche risk remained high at 4/5.

Météo-France, the national weather office, warned of a “very unstable snow cover especially above 1,800 to 2,000 metres.

“Avalanches can therefore be caused very easily by a skier or a walker and can involve very important volumes of snow.”

Val d'Isère village and ski slopes blanketed in snow.

The resort is a favourite with British skiers

The interior ministry “strongly” advised against off-piste activities and urged skiers and other mountain users to follow safety recommendations.

Bonnevie said: “It wasn’t an exceptional avalanche but mountains will never be a leisure park. There are risks that you have to accept and stay humble … and not let yourself get carried away after the first enchanted run. You have to ask yourselves the right questions at each descent.

“We can only urge people to be as cautious as possible in the coming days.”

Le Dauphiné Libéré, the regional daily, said a total of 15 people had been killed in avalanches in the Savoie in the French Alps since December.