Three women were found dead in a car near the Squaw Valley USA ski resort in California on Tuesday, possibly of carbon monoxide poisoning, authorities said.

Lacey Louann Sutton, 22, of Marysville, Sara Alice McCullah, 21, of Marysville, and a 17-year-old from Loma Rica were found by a Squaw Valley security guard in a parking lot near the resort at about 1:05 p.m., Sacramento station KCRA reported.

Snow was blocking the vehicle’s tailpipe, the Placer County Sheriff’s Department said, causing the toxic gas to enter the 1983 Oldsmobile sedan.

Lt. Allan Carter from the department said the engine was running at the time the bodies were found.

“It appears to be a tragic, accidental carbon monoxide poisoning incident,” Carter said.

Carter said the car was covered by what appeared to be a foot of snow.

The resort’s Web site reported it had received 3 feet of new snow from a storm system that moved in over the weekend and continued dropping snow through Tuesday.

Carter said it’s unknown if the three had been sleeping in the car.

Forensic autopsies will be performed by the Placer County Coroner’s Office to determine the exact cause of death.

Squaw Valley is known worldwide for hosting the 1960 Winter Olympics.