Placer County sheriff's Lt. Allan Carter says the women were apparently sleeping in the car, which was covered in snow.
Carter says the car's tailpipe appeared to be blocked by snow, allowing carbon monoxide to leak into the vehicle.
McCullah's mother, Cindy Walczak, said McCullah and Sutton had moved to the area to find work at the resort.
- Get more L.A. breaking news, weather, traffic and sports
- Have a news tip? Send your tips, video, or pictures