An avalanche buried several skiers on the busy slopes of the Swiss resort of Crans-Montana on Tuesday, police said, as scores of rescuers worked to dig out survivors.
The Nouvelliste, a local newspaper, quoted the commune's president Nicolas Feraud as saying that 10 to 12 people were believed to be trapped under the snow.
Contacted by Reuters, Feraud declined to comment on how many people he believed to be trapped.
"An avalanche occurred in the Plaine-Morte sector, search and rescue teams are on the site. Several people are buried," Valais cantonal police said in a Tweet.
In a separate statement, the Crans-Montana ski lift company said a ski patroller had set off the alarm at 1323 GMT and that "the circumstances of the incident are not yet known".
Philippe Magistretti, president of the ski lift company, told Reuters by telephone from the resort, which is scheduled to host two women's races this weekend: "About 100 rescue workers are on the site. We also have people from the army who were here ahead of the World Cup."
The mid-afternoon avalanche came as warm temperatures over the past week began melting heavy snow in the region.
It coincided with school holidays in some cantons, including Geneva, as well as overseas. Britain's Blackheath High School tweeted that all its students on a ski trip in the area were safe and well.
"There were about 8,000 skiers on the slopes, which is a good day," Magistretti said.
Two helicopters and rescue teams were at the site.
Marius Robyr, in charge of organising the World Cup races, was quoted in the daily Tribune de Geneve earlier on Tuesday as saying there was 1 to 1.5 metres of snow on La Nationale ski piste. He said it was closed to tourists ahead of the practice sessions and downhill and combined races.
"Our only 'enemy' is the sun," he said.