By Martin Goillandeau, CNN
(CNN) — A group of skiers on the final stretch of a three‑day backcountry trip in northern California were returning to the trailhead Tuesday morning when the snow above them suddenly broke loose, sending a wave of ice, rocks and debris crashing into them.
In its wake, six survivors were left scrambling to find more than half of their group who was missing and improvise shelter as they awaited rescue.
Emergency crews received reports of the avalanche in the Castle Peak area of Truckee, a town nestled in the rugged Sierra Nevada mountains near Lake Tahoe, around 11:30 a.m. and immediately began racing to the scene. But they were hampered by the same weather conditions the skiers faced: heavy snow and strong winds from a winter storm moving through the region and high avalanche warnings.
Nearly 12 hours later, at 10:40 p.m., six survivors had been rescued with “various injuries,” the Nevada County Sheriff’s Office said, noting two had to be transported to hospital.
“It took several hours for rescue personnel to safely reach the skiers and transport them to safety where they were medically evaluated,” the sheriff’s office added, as the search continues, “pending weather conditions,” for at least nine others still missing.
“It’s going to be a very slow, tedious process,” Nevada Captain Sheriff Russell Greene told CNN affiliate KCRA earlier Tuesday. Crews “have to be very careful accessing the area due to the fact that the avalanche danger is still very high.”
A race to reach the survivors
The area has been under the second highest level, a 4 of 5, of avalanche threat Tuesday, which continued into the early hours of Wednesday.
Blackbird Mountain Guides, the company leading the trip, said the group included 12 clients and four guides who had been staying at the Frog Lake huts since Sunday.
The sheriff’s office said a total of 15 people were on the trip, revising the number down. CNN has reached out to Blackbird Mountain guides for clarification.
“The leadership team at Blackbird Mountain Guides is working in full coordination with the Nevada County Sheriff’s Office and Nevada County Search and Rescue to support the ongoing rescue operation,” the company said in a statement. “Blackbird Mountain Guides is in direct contact with the emergency contacts of the affected clients and guides and is providing them with regular updates as verified information becomes available.”
On its website, the company advertises the ski trip to the Frog Lake Huts for those with an intermediate to advanced skill level.
Skiers spend their days navigating the mountain off-trail through steep terrain with the aid of guides, before returning to the huts for dinner, the company says.
Following the first call for help Tuesday, dozens of first responders approached the scene from multiple directions: ski rescue teams from Boreal Mountain Ski Resort and Tahoe Donner’s Alder Creek Adventure Center were dispatched, along with rescue crews from surrounding counties.
The rescuers – about 46 in total – approached the scene on skis and snowcats, with snowmobiles on standby, as they battled the harsh weather in the region, where snow was falling at a rate of 3 to 4 inches an hour Tuesday.
As the time ticked by, the survivors were told to “shelter in place as best they can in the conditions,” the sheriff’s office said.
The stranded skiers were communicating with rescuers through emergency beacons, Greene told KCRA, including some with the ability to send text messages.