Three skiers were killed Sunday when an avalanche swept them about 400 metres down an out-of-bounds canyon at a popular resort, but a fourth skier caught up in the slide was saved by a safety device, authorities said.

The four were among three groups of skiers — about a dozen people in all — making their way through 45 centimetres of fresh snow on the back side of Stevens Pass when the avalanche hit. Stevens Pass is in the Cascade Mountains, about 125 kilometres northeast of Seattle, Wash.

All were buried to some extent, but the men who died were swept approximately 450 metres down a chute in the Tunnel Creek Canyon area, King County Sheriff's Sgt. Katie Larson said.

Most of the other skiers, all well-equipped, were able to free themselves and rushed to dig out the victims. They performed CPR on the three men to no avail, Larson said.

The fourth skier who was swept down the mountain, a woman, appeared to avoid a similar fate because of the avalanche safety device she was wearing, Larson said.

Such devices include wearable airbags that can be deployed to help a person float atop an avalanche rather than being buried underneath it, or inflatable bags that create space between a person's mouth and the snow. It wasn't immediately known which kind the woman had, according to Chris Bedker, a deputy with the sheriff's search and rescue unit.

The men who died were believed to be in their 30s and 40s.

"Most of the people involved in this were well-known to the ski community up here, especially to the ski patrol," Bedker said. "It was their friends who they recovered."

Initial reports of the avalanche reached the sheriff's office just after noon, and for some time it wasn't clear whether the other skiers had also been swept up in the slide.

Snowboarder dies in separate incident

The Northwest Weather and Avalanche Center on Sunday issued a warning for high avalanche danger for areas above 1,525 metres, saying warmer weather could loosen surface snow and trigger a slide on steeper slopes. The elevation of the avalanche wasn't immediately clear.

At mid-afternoon, the temperature at the base of the ski resort was –4 C, with light winds and good visibility. The temperature at the top of the mountain was –5 C, according to the resort's website.

John Gifford, the ski area's general manager, said the resort has received 48 centimetres of snow in the past 24 hours. However, he said it wasn't snowing there Sunday afternoon.

Stevens Pass is one of the most popular outdoor recreation areas in the state. People flock there to go cross-country, backcountry and downhill skiing, as well as snowshoeing and backpacking.

Also Sunday, King County Sheriff's Sgt. Cindi West said a snowboarder was killed in a separate incident at the Alpental ski area east of Seattle. The snowboarder, a man, went over a cliff.

It's been a deadly winter in Washington's mountains. Four people disappeared in vicious storms while hiking and climbing on Mount Rainier last month.

Across the West, there had been 13 avalanche deaths this season as of Feb. 16, according to the Colorado Avalanche Information Center, which tracks avalanche deaths in the United States.

Avalanche deaths are more common in the backcountry than at ski resorts. Out of about 900 avalanche deaths across the U.S. since the 1950-1951 winter, 32 were within terrain that was open for riding at ski resorts, according to the Utah Avalanche Center.