STRATTON, Vt. (AP) – Two college students spending a night outdoors were killed in the collapse of their snow cave, apparently after a piece of heavy machinery dumped snow on their shelter while they slept, investigators said.

Jake Shumway, 19, and Robert Carr, 18, freshmen on spring break from Plymouth State College in New Hampshire, were found buried in the collapsed cave by friends Saturday morning at the Stratton Mountain ski resort.

Avid outdoorsmen, Carr, Shumway and a group of friends had gone to Stratton to watch the U.S. Open Snowboarding competition. They dug the cave at the edge of a parking lot, while the rest of their group spent the night sleeping in cars and campers.

Dan M. Davis, Windham County state’s attorney, said Monday that a bucket-loader dumped snow either on the snowbank or nearby.

“It may or may not have contributed to their deaths,” he said. “It certainly appears the cave collapsed as a result of the snow dumping.”

Davis said crews from the ski resort had been sanding the parking lot and moving snow around in preparation for the crowds of skiers. He said the snow dumping apparently took place between 5 a.m. and 6 a.m. Saturday, two to three hours before the men were discovered packed in snow in their sleeping bags.

Davis said he does not expect any criminal charges. “It certainly appears at this point in time to be accidental deaths,” he said.

Lewis Baldwin, an experienced hiker who works at the Appalachian Mountain Club’s Pinkham Notch hut, said snow caves can be very warm but must be constructed with care.

“It could be incredibly dangerous because like in an avalanche, if it collapses, the snow settles in like concrete,” he said. “Even if you were sleeping with a shovel, you probably couldn’t dig yourself out.”

Shumway, who died of asphyxiation, was the son of New Hampshire’s health and human services commissioner, Donald Shumway.

“Jake was full of energy and spirit. Hiking, camping, snowboarding and music were a big part of his life,” his parents said in a statement. “We take comfort in knowing he died doing something that he loved.”