Police say the 21-year-old Swiss athlete was struck early on Tuesday morning while filming above Orsieres, near Switzerland’s southern border with France and Italy. She had been following another snowboarder, who wasn’t caught in the avalanche.

Valais state police said in a statement that rescuers were able to free Balet, who had been wearing special safety equipment, but she died at the scene.

Balet recently won the Freeride World Tour. She was a member of watchmaker Swatch’s professional team. Freeride snowboarding takes place away from prepared routes and athletes are often at more risk of being caught in avalanches due to riding off piste.

Police say they have launched an investigation into the cause of the incident. “Despite immediate efforts to revive her, she died at the scene,” police said. “An investigation has been started to determine the causes of the accident.”

Balet had been wearing safety equipment including a device meant to help locate people in avalanches, as well as a helmet and an airbag designed to increase the chances of surviving a snow slide.

“I feel a great sadness, a sense of bitterness and above all a solidarity with those close to her,” Nicolas Hale-Woods, the Freeride World Tour founder, told AFP. He said it was a reminder that even when supervised, practising freeride snowboarding on a mountain carried “its share of uncertainty”.

“Estelle Balet was a naturally gifted shining star and demonstrated remarkable talent … bringing home her second title as World Champion just a few weeks ago in Verbier,” said the Freeride World Tour in a statement. “Our thoughts are with the family and friends of Estelle Balet as we send our deepest sympathy and condolences during this very difficult time.”

Balet, who grew up in the Swiss Alps, learned to ski as a tiny child. She began snowboarding at the age of 10 and was competing in freeride snowboarding as a teenager. While taking part in several major sporting competitions each winter, she also devoted a large part of her time to making snowboard films.

In a Swiss TV interview earlier this month, Balet was asked how she felt as she prepared to descend a mountain. She said if she was snowboarding for a film, she often felt “the fear of an avalanche”.