Il Nuovo Postiglione - Ten skiers missing in California avalanche

Officials say a group of 16 people -- four guides and 12 clients -- were caught up in the avalanche on Castle Peak in the Tahoe area late Tuesday morning.

Six have been accounted for, but mountain rescue teams battling treacherous conditions were still trying to reach them while also looking for the others, as snow continued to fall and daylight faded.

"Highly skilled rescue ski teams have departed from both Boreal Mountain Ski Resort and Tahoe Donner’s Alder Creek Adventure Center to make their way to the six known survivors, who have been directed to shelter in place as best they can in the conditions," the Nevada County Sheriff's department said.

"Rescue efforts remain in progress now with 46 emergency first responders. Weather conditions remain highly dangerous."

A powerful storm packing several feet (meters) of snow was continuing to pummel the Sierra Nevada mountain range, with forecasters warning of white-out conditions.

Experts had warned of the danger of avalanches on Tuesday, with the risk expected to extend into Wednesday.

"HIGH avalanche danger exists in the backcountry. Large avalanches are expected to occur Tuesday, Tuesday night, and into at least early Wednesday morning across backcountry terrain," the Sierra Avalanche Center said.

"HIGH avalanche danger might continue through the day on Wednesday."

The National Weather Service said parts of the Sierra above 3,500 feet (1,000 meters) could see up to eight feet (2.4 meters) of snow over the next 48 hours, with gusts of wind as strong as 55 miles (90 kilometers) an hour.

M.Dodaro--INP