A trio of skiers is likely buried under an avalanche near Anchorage, Alaska, that occurred Tuesday afternoon, but dangerous backcountry conditions have so far stymied recovery operations, officials announced.

They were likely killed under the weight of snow nearly as deep as a 10-story building, Alaska State Troopers said Wednesday.

If the deaths are confirmed, it would be the deadliest U.S. avalanche since three climbers were killed in a slide in Washington’s Cascade Range two years ago.