A 21-year-old Vancouver man is in hospital with serious injuries after he and his brother triggered an avalanche on Whistler Mountain, about 90 kilometres north of Vancouver.

The resort is the alpine venue of the Winter Olympics, but RCMP say the slide happened a few kilometres away from the competition sites, outside the boundaries of the resort.

"You'd have to take a couple of lifts from the top of the Olympic venue to even get close to this area," Staff Sgt. Steve LeClair of the Whistler RCMP detachment said Sunday.

"There's been no avalanche control in this beyond-boundary area by ski patrol, as opposed to the venue area, which is within the ski-area boundary and gets constant control."

LeClair said the men, aged 21 and 24, were skiing outside the marked boundaries of the Whistler-Blackcomb resort on Whistler Mountain's Piccolo peak Saturday afternoon when they were caught in the Class 3 slide, which in the five-level rating system is big enough to damage vehicles.

"One brother was 10 feet in front of the other and the one that was in the lead was the one that was caught in the slide," said LeClair.

Police say the younger man was swept 600 metres down the slope, suffering serious but non-life-threatening injuries. LeClair said he was hospitalized with broken ribs and possible internal injuries.

The men were not equipped for backcountry skiing but had apparently taken a recreational avalanche course.

"They were equipped to be day skiers, not to be backcountry skiers," said LeClair. "They said that they knew they were going beyond the boundary."

The injured man was not buried in the slide and his brother, after skiing down to check on him, had to walk back up the mountain to get reception for his mobile phone, said LeClair.

"He eventually alerted his father, who contacted ski patrol, who contacted us."

The pair was rescued by helicopter.

Four people have been killed by B.C. avalanches this winter. Last season, the worst on record, a total of 19 people were killed in avalanches in B.C.