Rescue teams combing through the backcountry of California's Lake Tahoe region say they have found the bodies of eight skiers who went missing in an avalanche on Tuesday.

The search for a final missing skier continues, but that person is presumed dead, Nevada County Sheriff Shannan Moon said at a news conference on Wednesday.

Officials said one of the deceased was the spouse of someone on one of the search-and-rescue teams, making continued rescue efforts "challenging emotionally".

Fifteen skiers were reported missing on Tuesday after a "football-field" sized avalanche came barreling down in the Castle Peak area around 11:30 PST (19:30 GMT). Six have been rescued.

"I want to offer my condolences to the family in this very trying time," Placer County Sheriff Wayne Woo said on Wednesday.

The bodies of the eight dead skiers are still trapped in the snow and can't yet be recovered due to "pretty horrific" conditions, officials said.

Since the avalanche, another 3ft (.9m) of snow has fallen on the area, Tahoe National Forest supervisor Chris Feutrier said.

"The hazard remains high," he said.

Once the bodies are recovered, they will be transported to the Placer County morgue.

Families of the deceased have been notified. Authorities have not yet released any of their names.

Sheriff Woo said the rescue operation was a joint effort involving two teams and roughly 50 crew members who had to traverse "extreme weather conditions" using specialised equipment.

At 17:30 local time on Tuesday, search teams arrived to an area roughly two miles (3.2km) from where survivors were sheltering in make-shift tents, and had to ski in from there.

Two of the six survivors had to be carried back and "could not walk because of the injuries they sustained during the avalanche", Sheriff Moon said. They were taken to hospital with non-life-threatening injuries.

Among the survivors, one was a guide and five were clients of the Blackbird Mountain guided tour.

The entire ski group consisted of a mix of 11 recreational skiers and four ski guides.

The avalanche on Tuesday occurred as they were making their way back at the end of a three-day trip.

California Governor Gavin Newsom's office said in a post on X that state authorities were "co-ordinating an all-hands search-and-rescue effort" with local emergency teams.

Conditions on Wednesday remained dangerous, multiple officials said, with Woo describing the climate as "treacherous".

"Avoid the back country," he said. "Please allow us to focus all of our resources on continuing to recover these bodies for the family and bring them home."

The avalanche that trapped the skiers was rated as a D2.5 on a scale of D1 to D5, Sierra Avalanche Center Forecaster Steve Reynaud told local outlet ABC News 10.

The Boreal Mountain Ski Resort, which is near where the accident occurred, has reported over 30in (76cm) of snowfall since Tuesday.

The resort decided to close on Tuesday because of high winds and low visibility.

The storm has also closed several highways, including Interstate 80 and Highway 50.