Eight skiers have been found dead and one is still missing after an avalanche in the US.

The skiers were part of a tour group returning from a three-day trip in northern California’s Sierra Nevada country near Lake Tahoe when the avalanche struck at Castle Peak.

Nevada County Sheriff Shannan Moon said in a press conference this morning six survivors were able to contact emergency services.

Eight skiers have been found dead after an avalanche near Lake Tahoe in the US. (9News)

The survivors, consisting of one man and five women aged 30 to 55, were able to locate two of their fellow travellers, who were already dead, before emergency services arrived.

Two of the survivors were too badly injured to move on their own but all six were rescued.

Since then, authorities have confirmed that eight of the nine remaining missing skiers had been found dead.

Six survivors have also been rescued. (9News)

Moon said the weather and further avalanche risks were hampering the search for the final missing person.

“Extreme weather conditions, I would say is an understatement,” she said.

Families have been told the operation is now considered a recovery, meaning the final missing skier is not expected to be found alive.

The area near Donner Summit is one of the snowiest places in the western hemisphere and until just a few years ago was closed to the public.

READ MORE: Ute found after man killed in horror wrong-way crash on major highway

Donner Summit is known for heavy snowfall and grim history. (Getty Images/iStockphoto)

It sees an average of nearly 10 metres of snow a year, according to the Truckee Donner Land Trust, which owns a cluster of huts where the group was staying near Frog Lake.

The Sierra Avalanche Centre warned that the risk of avalanche remains high and advised against travel in the area.

Heavy snowfall and gale-force winds in recent days left the snowpack unstable and unpredictable, and more snow was predicted to fall, the centre said.

Nevada County Sheriff Captain Russell Greene said authorities were notified about the avalanche by Blackbird Mountain Guides, which was leading the expedition, and the skiers’ emergency beacons.

Of the survivors, one was a guide and five were clients.

The skiers were on the last day of a back-country skiing trip and had spent two nights in the Frog Lake huts, said Steve Reynaud, an avalanche forecaster with the Sierra Avalanche Centre. He said the area requires navigating rugged mountainous terrain. All food and supplies need to be carried to the huts.

Reaching the huts in winter takes several hours and requires backcountry skills, avalanche training and safety equipment, the land trust says on its website.

Blackbird Mountain Guides said in a statement said the group, including four guides, was returning to the trailhead when the avalanche occurred.

“Our thoughts are with the missing individuals, their families, and first responders in the field,” Blackbird said in a statement. The company said it is helping authorities in the search.

“The leadership team at Blackbird Mountain Guides remains fully engaged in assisting the search and rescue efforts on the ground as we navigate this incredibly difficult situation alongside those involved,” an update to the original statement read.

Several Tahoe ski resorts had been fully or partially closed due to the weather. Resorts, which use controlled explosions and barriers to manage avalanche threats, were not expected to be at as high of a risk as the back country, the centre said.

The area near Donner Summit was closed for nearly a century before the land trust and its partners in 2020 acquired Frog Lake, which is framed by 300m-high cliffs.

Donner Summit is named for the infamous Donner Party, a group of pioneers who resorted to cannibalism after getting trapped there in the winter of 1846-1847.

In January, an avalanche in the region buried a snowmobiler and killed him, authorities said. Each winter, 25 to 30 people die in avalanches in the US, according to the National Avalanche Centre.

With Associated Press.