Eight backcountry skiers were confirmed killed and a ninth was presumed to have perished when their tour group was overtaken by a football-field-sized avalanche in California’s Sierra Nevada mountains on Tuesday, in the deadliest US avalanche in 45 years, authorities said.

Six survivors were rescued after search teams on skis fought through blinding snow, darkness, treacherous terrain and gale-force winds to reach them in the rugged Castle Peak area near Truckee, California, about 10 miles (16 km) northwest of Lake Tahoe.

The group of 15 skiers, including four guides from outfitter Blackbird Mountain Guides, was heading back to a trailhead in heavy snow after a three-day excursion when the avalanche struck around 11:30 a.m. PT on Tuesday.

The surviving skiers, who took refuge in a makeshift shelter constructed partly from tarpaulin sheets after the avalanche, used emergency beacons and text messaging to communicate their location to rescuers. One of the guides was among the survivors, Nevada County Sheriff Shannan Moon said at a press conference.

Two rescue teams, totalling about 50 people were dispatched from the Boreal Mountain Ski Resort and the Tahoe Donner resort’s Alder Creek Adventure Center and approached the avalanche zone from the south and north.

High risk of avalanche

The rescuers themselves faced life-threatening conditions, with the risk of further avalanches still high after a winter storm dropped several feet of fresh, unstable snow in recent days. Responders were able to get within two miles (3.2 km) of the avalanche site on a snowcat vehicle, then switched to skis to lessen the risk of triggering another deadly slide.

“Extreme weather conditions, I would say, is an understatement,” said Moon, whose office helped oversee the search mission.

An adjacent stretch of the US Interstate 80 highway had been closed during the rescue operation due to zero visibility from the storm.

Bodies of eight skiers were located but will be recovered at a later date when weather permits, while a ninth skier from the group remained missing and was presumed dead, authorities said.

One of the deceased skiers was the spouse of a search-and-rescue team member, authorities said. An injured skier was being treated in a hospital with non-life-threatening injuries.

The tour group, which included nine women and six men, had been staying at the Frog Lake Backcountry Huts near Donner Summit northwest of Truckee, at about 7,500 feet elevation (2,300 meters). The area is a popular destination for backcountry skiers.

In a typical winter, the mountain receives more than 400 inches (10.16 m) of snow, making it one of the snowiest places in the Western Hemisphere.

Moon said the storm and avalanche danger were predicted and her office was 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 Wednesday.

Comparatively high casualty toll

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 tallied six US avalanche fatalities so far this season before Tuesday’s disaster. One person was killed by an avalanche in the Frog Lake area in January.

Tuesday’s calamity was notable for its comparatively high casualty toll. It marked the greatest loss of life on record in the US from a single avalanche since a 1981 ice slide on Mount Rainier in Washington state killed 11 people as they were climbing the Ingraham Glacier, according to the Colorado centre’s director, Ethan Greene.

In 1982, seven people died in a massive avalanche that struck the Alpine Meadows ski resort in California, also near the northwestern shore of Lake Tahoe.

Greene said it was far too soon to understand all the circumstances around the latest disaster but noted the heavy snowfall and avalanche dangers were “well forecast.”

Venturing out on skis in avalanche country in the midst of a major storm is “not something we would be advising people to do, especially in a guided group.”

He also said ski groups normally try to limit exposure to a particularly slide-prone section of terrain to no more than one skier at a time so that if one person becomes trapped in an avalanche, others in the group can work to quickly locate and dig out the victim.

Blackbird issued a statement on Tuesday saying it was working with authorities to support the rescue operation. The company referred questions to local authorities on Wednesday.

Blackbird was founded in 2020 and operates in California, Washington state and British Columbia in Canada as well as numerous popular skiing spots abroad, according to its website. The company provides guided ski trips, alpine climbing trips and avalanche education.