Avalanche engulfs around a dozen people at Swiss ski station

An avalanche at a ski station in the Swiss Alps engulfed up to a dozen people on Tuesday, a local official and media reports said, with hopes fading of finding survivors in a disaster that hit a resort busy with skiers on school holidays.

The avalanche hit the Plaine-Morte ski slope in Crans-Montana, southwestern Switzerland, in the early afternoon, local police said in a tweet. A local newspaper, Le Nouvelliste, quoted the head of Crans-Montana's municipal government, Nicolas Feraud, as estimating that "between 10 and 12 people" remained buried under the snow.

There was no official confirmation of any deaths.

"We are shocked and hope for good news about these people," Feraud was quoted as saying.

A first attempt at locating victims using sniffer dogs was unsuccessful, a rescue worker told Le Nouvelliste, with four helicopters joining the search from the air.

Pierre Huguenin, of the Institute for Snow and Avalanche Research, described the snow in the area as damp and dense.

"These kinds of conditions complicate search efforts," he told the daily Le Temps.

According to statistics from his institute, after 15 minutes under an avalanche, the chances of survival are no more than 50 percent. In a statement, the Crans-Montana resort said it was unable to confirm any victims.

Le Nouvelliste quoted several unidentified witnesses as saying that four people had been pulled out of the snow but their condition was unclear. The paper said the avalanche swept over 300 to 400 metres (yards) of the lower section of the Kandahar slope.

It quoted rescue workers as saying the snow was compacted and more than two metres (seven feet) thick.

Crans-Montana's website had listed the risk of an avalanche at two on a scale that runs from one (lowest risk) to five.

As the victims were on a designated ski slope, they were unlikely to have detector equipment to help rescue workers locate them. The vast majority of deadly avalanches in the Alpine nation hit people skiing off-piste.

"We don't know yet whether the avalanche detached by itself or was set off by skiers, or a rockfall," Swiss avalanche expert Robert Bolognesi told the daily 20 Minutes.

Plaine-Morte, at an altitude of about 3,000 metres (9,800 feet), is the highest ski slope at Crans-Montana.