The other skiers in the group were able to free themselves from the snow, and quickly made their way to dig out those still buried. They performed CPR on the victims but were unable to revive them, Sgt. Larson told the AP.
Reports of the avalanche reached the sheriff's office shortly after noon and ski patrol officials had reached the group by 12:50 p.m.
Stevens Pass is one of the most popular outdoor recreation destinations on the Northwest, particularly for skiing, snowboarding and backpackers.
About two hours south at Snoqualomi Pass, a snowboarder was killed after another avalanche struck Sunday and he went over a cliff. Rescue video taken earlier this month shows a man being rescued when an avalanche buried him next to his snowmobile.
There have now been 13 avalanche deaths this winter season, according to the Colorado Avalanche Information Center. Experts have said that a weak base layer of snow caused by a dry winter has lead to the dangerous conditions.