The avalanche swept the Castle Peak area of Truckee, California, about 16km north of Lake Tahoe, at about 11:30am on Tuesday, engulfing a group of 16 skiers, according to a Facebook statement posted by the Nevada County Sheriff's Office.
Search and rescue crews were dispatched after someone called 911 to report the emergency.
The group consisted of four ski guides and 12 clients. At least six survived and remained at the avalanche site awaiting rescue, while the others were unaccounted for, the statement said.
Ashley Quadros, a spokesperson with the Nevada County Sheriff's Office, said the six survivors were asked to shelter in place "as best they can" to wait for search and rescue ski teams reach them.
If all 10 of the missing skiers should perish, the incident would rank among the deadliest single avalanches on record in the United States. The Colorado Avalanche Information Center has tallied six US avalanche fatalities so far this season.
Avalanches have claimed an average of 27 lives each winter in the US over the past decade.
The sheriff's office, the sheriff's Search & Rescue team and a crew with the California Department of Forestry and Fire Protection combed the area of Castle Peak, which is northwest of Lake Tahoe, Quadros said.
California is being walloped this week by a powerful winter storm carrying treacherous thunderstorms, high winds and heavy snow in mountain areas.
According to the Sierra Avalanche Center of the Tahoe National Forest based in Truckee, the area in the Central Sierra Nevada, including the Greater Lake Tahoe region, was facing high avalanche danger in the back country with large slides expected to occur Tuesday and into Wednesday.
Weather conditions remain highly hazardous in the Sierra back country slopes, with additional avalanche activity expected through Tuesday night and into Wednesday, according to the statement.
California Governor Gavin Newsom was briefed on the avalanche, and state authorities were "co-ordinating an all-hands search-and-rescue effort" in conjunction with local emergency teams, his office said.
The dangerous conditions were caused by rapidly accumulating snowfall piling on already fragile snow pack layers coupled with gale-force winds.
Several ski resorts around Lake Tahoe were fully or partially closed due to the extreme weather.
The resorts along highways have avalanche mitigation programs and were not expected to be at as high of a risk as the back country where travel in, near, or below the avalanche terrain was strongly discouraged, the centre said.
"It's particularly dangerous in the back country right now just because we're at the height of the storm," said Brandon Schwartz, Tahoe National Forest lead avalanche forecaster at the centre.
Experts rely on people who witness an avalanche or its aftermath to know when and where an avalanche has occurred, Schwartz said.
28°C