Vaud cantonal police said the avalanche unleashed a snow slide about 200 metres (650 feet) long and 60 metres (195 feet) wide.
A large-scale search involving a helicopter, 30 rescuers, dogs and gendarmes produced no results on Wednesday evening but was set to resume on Thursday morning.
Les Diablerets, lying between Lake Geneva and Gstaad at an altitude of 1,200 metres (3,935 feet), is known as a centre for skiing, snowboarding and other adventure sports.
Member comments