TRUCKEE, Calif. – All nine victims in the Castle Peak avalanche on Feb. 17 reportedly died of asphyxia.

The information is based on partially redacted reports the Nevada County Coroner’s Office shared with the San Francisco Chronicle on Thursday, Aug. 6. The Sun is awaiting copies of the reports from the coroner’s office and has not independently verified this information.

Asphyxiation occurs when the body does not receive enough oxygen. During avalanches, asphyxia can occur in three ways: when the airway is obstructed by snow, when the chest cannot expand due to snow weight and compaction, and, finally, due to hypoxia resulting from rebreathing the same air in a confined space.

Asphyxiation is the leading cause of avalanche fatalities. One study found they account for 75% of fatalities.

Studies have also found that burial depth plays a critical role in asphyxia-related fatalities. Victims buried deeper than two meters (around 6.5 feet) have a probability of survival of only 10%, while those buried less than half a meter (around 1.5 feet) have an 80% survival rate.

The victims buried in the Castle Peak avalanche were buried 5-8 feet below the surface.