Updated

Snowfall and fog were hampering a search in the Swiss Alps on Monday for three people believed trapped after avalanches killed at least four skiers and a rescue doctor, officials said.

The worst incident occurred Sunday, when two avalanches hit a group of skiers, then the rescuers who came to their aid in the Diemtig Valley about 25 miles south of the capital, Bern.

Eight people were pulled from the snow alive, but three -- two skiers and the rescue doctor -- later died in the hospital of their injuries, police spokeswoman Ursula Stauffer told The Associated Press by telephone. Another skier was recovered dead.

"Rescuers haven't been able to resume their search today because the helicopter can't get close to the site due to the bad weather," said Stauffer.

She said the three missing skiers were part of a large group that was skiing off-piste in the Chummli area of the Diemtig Valley when an avalanche buried one member of the party around midday Sunday. Rescuers who arrived to help the skiers about half an hour later were hit by a second avalanche at the same spot, said Stauffer. Officials subsequently launched a massive operation involving eight helicopters and 100 rescuers in an attempt to save their colleagues and the missing skiers.

Stauffer declined to identify the victims of the disaster until a news conference scheduled late Monday afternoon.

Bernhard Scherz, an official with the Rubigen ski club who took part in the rescue, told Swiss Web site 20 Minuten Online that one of those recovered alive from the avalanche was an Englishman. He had been buried under 8 feet (2.5 meters) of snow. But an official at the British Embassy said British citizens weren't known to have been injured or killed in the avalanche, according to information provided by cantonal police. The official spoke on condition of anonymity because she wasn't authorized to make public statements.

Separately, two skiers were buried in another avalanche Sunday near the town of Verbier close to the borders with France and Italy. One skier was killed but the skier's guide was rescued alive, police in the southern canton of Valais said.

The start of the ski season and heavy snowfall in recent days have prompted officials to warn of a heightened avalanche risk in the Swiss Alps.