PARIS — An avalanche on Mont Blanc swept two skiers to their deaths and left another injured, while a hiker was killed on another slope in the French Alps, according to local authorities.

The avalanche Thursday swept through an off-piste area of the Saint-Gervais-les-Bains ski resort at an altitude of 2,300 meters (7,545 feet), the administration for the Haute-Savoie region said in a statement.

Dozens of mountain rescuers set out to search for skiers trapped, finding a man and a women dead and one person injured, and rescuing five others, the administration said.

An investigation was opened into the cause of the avalanche.

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Saint-Gervais Mayor Jean-Marc Peillex said the weather conditions were too unstable for such risky outings.

“It rained, it snowed, it was warm. There are enough marked paths to ski on,’’ he told BFM television. ‘’It’s terrible what happened. A family is decimated, and we are very sad in Saint-Gervais.’’

To the north, a 31-year-old hiker was found dead after falling on the slope of the Ecrins mountain range. The hiker had veered away from hiking paths to look at mountain goats with a friend, local broadcaster France-Bleu cited rescuers as saying.