The Nevada County Sheriff's office on Friday conducted an aerial survey of the avalanche site near Castle Peak.

The avalanche, the deadliest in California history and fourth deadliest in U.S. history, killed at least eight people and left a ninth missing.

A winter storm warning forecast up to 8 feet of snow in California’s Lake Tahoe Region and the avalanche conditions were considered “very dangerous.”

Legal experts say a criminal investigation announced into whether negligence played a role in a deadly California avalanche could hinge on key decisions by guides leading the ill-fated ski trip.

The Castle Peak region, site of the avalanche, is a backcountry area in the Sierra Nevada, popular year-round and easily accessible from the interstate that connects the San Francisco Bay Area to the Lake Tahoe region.

Helicopters flew over the avalanche site to assess the avalanche danger and the snowpack. Later, they began setting off explosives to trigger small snow slides.

The Truckee community is mourning the six women killed in the deadly Nevada County avalanche. The victims lived in the Bay Area, Truckee–Tahoe region and Idaho.

Officials in Nevada County, Calif., are investigating whether there could have been criminal negligence involved in the disaster that killed at least eight people.