Bodies of all 9 missing skiers recovered after deadly avalanche; criminal negligence investigation launched, sheriff's office

An investigation is underway to determine if the deadly avalanche incident in California’s Sierra Nevada Mountains -- that left several people dead -- involved criminal negligence, according to the Nevada County Sheriff's Office.

Meanwhile, at a press conference on Saturday, officials announced that the bodies of all nine missing skiers had been recovered following the backcountry avalanche occurred on Castle Peak on Feb. 17. Over the past two days, search and recovery teams were able to recover all nine bodies, officials said, for the first time identifying all the victims.

At the press conference Saturday, authorities provided an update on the search and recovery effort, but Nevada County Sheriff Shannan Moon did not address the investigation.

Asked about the decision-making of the group amid "high" avalanche danger warnings issued by the Sierra Avalanche Center, Moon stressed that officials only had preliminary information so far, but said the group was on the last day of a three-day tour and "they did decide to leave early to try to get off the mountain early."

As for other decisions, Moon said authorities needed more time for the investigation, "just so that we can truly know what happened."

Officials said the avalanche was D2.5 -- strong enough to knock down a person, almost strong enough to knock down a house and the path of the avalanche was the length of a football field.

Many of the victims in Tuesday’s historically deadly avalanche on Castle Peak were mothers from Marin County, California, whose children attend Sugar Bowl Academy, a nearby private boarding school designed for skiing, according to multiple sources. There were also several guides who lost their lives.

"This was an enormous tragedy, and the saddest event our team has ever experienced. In addition to mourning the loss of six clients, we also mourn the loss of three highly experienced members of our guide team. We are doing what we can to support the families who lost so much, and the members of our team who lost treasured friends and colleagues," Zeb Blais, the founder of Blackbird Mountain Guides, said in a statement Wednesday.

The California Division of Occupational Safety and Health has also confirmed to ABC News that it has opened an investigation into the avalanche incident "involving guides employed by Blackbird Mountain Guides LLC near Castle Peak Mountain in Truckee," it announced Thursday.

Families of the dead skiers told ABC News that they have "many unanswered questions," saying the mothers killed in the avalanche were "experienced backcountry skiers."

Six people survived the avalanche -- four men and two women -- and were rescued by crews after sheltering under a tarp for hours amid "highly dangerous" conditions, authorities said.

All of the guides were trained or certified in backcountry skiing by the American Mountain Guides Association and were instructors with the American Institute of Avalanche Research and Education, according to Blais.

A major winter snowstorm and "high" avalanche danger warnings in the backcountry were issued on Tuesday by the Sierra Avalanche Center.