Eight of nine skiers missing after an avalanche have been found dead in California’s mountains amid a raging blizzard and dangerous storm conditions.

Nevada County Sheriff Shannan Moon told media on Thursday morning (AEDT) that the bodies were found fairly close together in the state’s Lake Tahoe region.

The avalanche was estimated to be the size of a football field and happened in a week when California was being walloped by a treacherous winter storm, bringing extreme snowfalls and high winds.

An avalanche warning had been issued for the Central Sierra Nevada, including the Greater Lake Tahoe region, where the skiers were on a three-day adventure.

The Los Angeles Times reported that the death count would make it the worst avalanche in the state’s modern history.

A group of 15 had set out on a self-sufficient skiing trek, which involves navigating and carrying food and supplies between huts, when disaster struck.

Six skiers who were trapped by snow and ice were rescued in extreme conditions. Nine others from their tour group were missing.

Two of the six were taken to a hospital for treatment, the Nevada County Sheriff’s Office said.

There are questions about why the group was skiing in known avalanche areas, despite a week of warnings.

Rescuers head out to the avalanche from Soda Springs, California. Photo: AAP

Search and rescue crews were sent to Frog Lake in the Castle Peak area, north-west of Lake Tahoe, after an emergency call reporting an avalanche and people buried.

It took crews several hours to reach the skiers and take them to safety, where they were evaluated by the Truckee Fire Department.

Steve Reynaud, from the Sierra Avalanche Centre, said the skiers were on a trip that required navigating “rugged mountainous terrain” for up to six kilometres while carrying all their food and supplies.

Nevada County Sheriff Captain Russell Greene said authorities were notified about the avalanche by the ski tour company that led the expedition, Blackbird Mountain Guides, and by emergency beacons carried by the skiers.

Rescuers had to approach the scene of the avalanche cautiously because of the danger of further avalanches.

Heavy snow in Soda Springs, California. Photo: AAP

Blackbird Mountain Guides said in a statement on its website that it was co-ordinating with authorities on the rescue operation.

“It’s particularly dangerous in the backcountry right now just because we’re at the height of the storm,” said Brandon Schwartz, Tahoe National Forest lead avalanche forecaster at the Sierra Avalanche Centre.

The centre issued an avalanche warning for the area in the Central Sierra Nevada, including the Greater Lake Tahoe region, starting early on Tuesday (local time) with large slides expected into Wednesday.

The town of Soda Springs, near the avalanche site, had more than 70 centimetres of snow in 24 hours.

The dangerous conditions were caused by rapidly accumulating snow piling on fragile snow-pack layers coupled with gale-force winds.

The storm wreaked havoc on roads from the Sierra Nevada to Sonoma County, with traffic halted temporarily in a highway due ot spin-outs and crashes.

Several Tahoe ski resorts were fully or partially closed due to the weather.

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 avalanche terrain was strongly discouraged, the centre said.

-with AAP