MT. HOOD, Oregon -

Search teams are resuming their rescue efforts for a snowboarder trapped following an ice tunnel collapse..

Authorities say the outlook is dim for a snowboarder, identified only as an out-of-state visitor in his mid-20s, who was traveling with five other snowboarders when a piece of ice the size of a school bus fell on him.

"This is clearly not a good-looking situation when it comes to survivability," said Sgt. Pete Hughes, a spokesman for the Hood River County Sheriff's Office.

The snowboarders had been taking photos of themselves inside the ice tunnel at White River Glacier, about 8,100 feet in elevation, when the collapse occurred just after 4 p.m. The site is on the mountain's south slope outside the ski area, officials said.

The other snowboarders escaped without injury.

Search teams are coming back with "whatever we can get" in terms of manpower and equipment, said Rick Ragan, of Hood River County Crag Rats. Six people had been using hand tools to clear overhanging ice so it doesn't pose danger to morning rescuers.

Only part of the ice tunnel collapsed, leading search teams to worry that the rest would follow. Chain saws could be needed to cut through the ice, Ragan said.

Members of the Crag Rats and Portland Mountain Rescue responded, with more searchers on standby.