Recovery efforts near Donner Pass stalled by severe weather; 1 still missing.

Law enforcement officers gather outside the Nevada County Sheriff's Office in Truckee on Wednesday after an avalanche on Tuesday left eight skiers dead. Six survived and one is missing. Ray Chavez - Bay Area News Group.

Members of a rescue team in Soda Springs make their way through snow left by a severe storm Tuesday. COURTESY OF NEVADA COUNTY SHERIFF'S OFFICE.

An unidentified member of the Nevada County sheriff's search and rescue team returns to the sheriff's office during the search for avalanche victims in the Castle Peak area Wednesday. Hector Amezcua -The Sacramento Bee/TNS.

By Grant Stinger and Caelyn Pender | Bay Area News Group

Eight skiers lay buried on a Sierra mountainside Wednesday, their bodies marked by poles stuck into the snow, a day after a powerful avalanche tore through backcountry terrain near Donner Pass.

One more person remained missing.

High avalanche danger and blizzard conditions prevented crews from immediately recovering the dead, authorities said, forcing families to wait as rescuers monitored unstable slopes above the debris field.

The disaster is the deadliest avalanche in California since 1982, when seven people were killed at Alpine Meadows Ski Resort. Tuesday's slide, which struck near Castle Peak north of Interstate 80, claimed eight lives, surpassing that toll and marking one of the worst backcountry tragedies in state history.

"Avoid mountain travel; it's treacherous," Placer County Sheriff Wayne Woo told reporters Wednesday morning. "Avoid the backcountry. Please allow us to focus all of our resources on continuing to recover these bodies for the family and bring them home."

The avalanche struck Tuesday morning as a guided group of 15 skiers was returning from the Frog Lake backcountry cabins on the final day of a planned three-day trek, Nevada County Sheriff Shannan Moon said.

Initially, investigators believed 16 people were on the trip - four guides and 12 clients - but one person decided not to go, Moon said.

The trip was led by Blackbird Mountain Guides, a Truckee-based outfitter. Avalanche danger was forecast to be high as a severe winter storm blanketed the region with heavy snow atop weak layers formed during a long, dry January.

Investigators are beginning to examine the circumstances of the outing, Moon said, though she emphasized that the guide company has been cooperative. Calls to the company were not returned Wednesday.

The SierraAvalanche Center said heavy new snow overloaded a fragile snowpack, creating volatile conditions. It remains unclear what triggered the slide.

One member of the group apparently shouted a warning moments before the avalanche struck, officials said.

Survivors used an iPhone's SOS feature to contact emergency responders and transmit their location. Authorities quickly assembled about 50 trained rescuers, who approached from both the north and south.

A snowcat transported crews within 2 miles of the site. From there, responders skied through worsening weather, arriving around 5:30 p.m. to what Moon described as "extreme conditions."

They found a debris field roughly the size of a football field.

Rescuers evacuated the six survivors by snowcat. Two were hospitalized with injuries that were not life-threatening. Of those who survived, one was a guide and five were clients, Moon said.

Eight bodies were located in the avalanche debris, said Chris Feutrier, forest supervisor of the Tahoe National Forest. The ninth missing skier has not been found. The bodies remain on the mountainside, awaiting safer conditions for recovery.

"It's not a resource issue as we speak," she said. "It's a weather condition and safety issue for our response teams."

Authorities have not released the victims' names out of respect for their families. They came from several states, officials said. One of the dead was the spouse of a member of Tahoe Nordic Search and Rescue, Woo said.

"They're still reeling," Moon said of the families. "I could not imagine what they're going through."

The avalanche occurred in a remote stretch of terrain near the summit of Donner Pass and the Pacific Crest Trail, an area prized for its beauty and solitude but known for steep slopes and avalanche exposure.

The Sierra Avalanche Center warned Wednesday that natural avalanches remain likely and that human-triggered slides "large enough to bury or injure people are very likely." More snow was forecast for the Tahoe region, further complicating recovery efforts and prompting authorities to urge people to stay out of the backcountry.