An avalanche in southern Montana buried three snowmobilers from North Dakota, killing a 33-year-old man.

The Park County Sheriff's Office said two of the snowmobilers were able to dig themselves out Saturday from the slide north of Cooke City on the Montana-Wyoming line. The victim and his companions have not been identified.

Undersheriff Clay Herbst said five people were riding snowmobiles when one of the riders got stuck. That started an avalanche, which buried the three riders.

Authorities said all riders were experienced, and had avalanche beacons, shovels, and backpacks with inflatable airbags. Authorities did not say if the airbags were deployed.

The Gallatin National Forest Avalanche Center warned people in the backcountry about dangerous conditions. Officials said Sunday that continuing snowfall and strong winds have made the snowpack unstable and natural and human-triggered snow slides are likely.

The warnings cover the mountains near Cooke City, the Madison Range, the Gallatin Range, the Lionhead area near West Yellowstone and the Bridger Range.