Rescuers on skis were able to reach six survivors amid an intense winter storm that has dropped heavy snow on the high Sierra in recent days. One skier remains unaccounted for.
The avalanche - the length of a football field, according to authorities - struck in the Castle Peak area of Truckee, California, about 16 kilometres north of Lake Tahoe, on Tuesday morning, local time.
It engulfed a group of backcountry skiers who were completing a three-day guided excursion.
One of the rescued skiers is still being treated in hospital with non-life-threatening injuries, Nevada County Sheriff Shannan Moon said at a press conference.
The survivors had taken refuge in a makeshift shelter, constructed partly from tarpaulin sheets, and communicated with rescuers via radio beacon and text messaging.
Two rescue teams totalling about 50 members faced "extreme" conditions, Moon said, including blinding snow and gale-force winds.
A team was able to use a snowcat vehicle to get within 3km of the survivors and then ski to the accident site.
The eight dead skiers were found with their beacons active, and their bodies will be recovered when weather permits, authorities said. One was married to a member of the search-and-rescue team.
The group of skiers had been finishing a three-day excursion with Blackbird Mountain Guides at the time of the avalanche.
The tour group included four guides and 11 clients, who stayed at the Frog Lake Backcountry Huts located near Donner Summit just northwest of Truckee, at about 2300m.
In a typical winter, the mountain receives more than 10 metres of snow, making it one of the snowiest places in the western hemisphere.
Moon noted that forecasts widely predicted the storm and attendant avalanche danger and said her office is still talking with the guide company about its decision to take people out.
The Sierra Avalanche Centre extended the avalanche warning it issued on Tuesday, saying a "high" danger might continue throughout the day on Wednesday.
Blackbird issued a statement on Tuesday saying it was working with authorities to support the rescue operation.
The company was founded in 2020 and operates in California, Washington state and British Columbia as well as numerous popular skiing spots abroad, according to its website.
The company provides guided ski trips, alpine climbing trips and avalanche education.
Avalanches have claimed an average of 27 lives each winter in the United States over the past decade, according to the Colorado Avalanche Information Centre, which had tallied six US avalanche fatalities so far this season before Tuesday's disaster.
