Six climbers are missing on a peak of Mont Blanc and search helicopters are flying over the area, rescue services said.
August is the height of the climbing season on Europe's tallest mountain, where even in the warmest months fierce snowstorms can strike quickly.
Several mountaineers have died already this summer, and local officials say they fear people are coming to Mont Blanc ill-prepared for the dangers.
The rescue service, based in the city of Chamonix, said the six disappeared early this morning as they were trying to reach the Aiguille d'Argentiere, which tops out around 3,900m.
Mont Blanc, in addition to its primary peak, contains some 200 summits.