Crews have recovered the bodies of nine backcountry skiers killed by an avalanche on Castle Peak near Lake Tahoe, California, concluding a search hindered by heavy snowfall.

The avalanche struck on the last day of the group’s three-day tour, with six survivors calling for help after witnessing the sudden slide.

Rescue efforts were slowed by dangerous conditions, requiring helicopters, ropes, and snowcats, as well as controlled snow releases to stabilize the area.

Nevada County Sheriff Shannon Moon praised the combined efforts of multiple agencies and volunteers in the recovery operation, the AP has reported.

Officials said the terrain will remain closed to visitors until mid-March while the investigation into the avalanche continues.