One of the two skiers who had to be dug out of the snow after being swept downhill by an avalanche over the weekend was a four-year-old, CTV News has learned.

A source told CTV News that the boy and his father were skiing at Whistler Blackcomb when they were hit by an avalanche triggered by another group of skiers at a higher elevation. The avalanche was reported shortly before 1 p.m. Sunday, in an area outside of the ski boundary in the Blackcomb Glacier area.

Staff at Whistler Blackcomb said it was caused by backcountry skiers returning to the ski area from Corona Bowl, an out-of-bounds area near the glacier.

The avalanche was measured at 1.5, falling between being relatively harmless and being able to bury, injure or kill a person. In this case, the boy and his father were swept downhill and buried, but were able to dig themselves out with the assistance of passersby.

"People were quick to respond. Within two minutes there was 10 people over there digging," witness J.J. West told CTV.

Neither was injured, nor did they need to help from a rescue crew.

Ski patrol responded with an avalanche service dog, and searchers were able to determine that no one else was involved. Staff investigated the incident and deemed the area safe to remain open.

The incident prompted a reminder from the resort to those thinking of heading into backcountry. Skiers and snowboarders drawn by the lure of making fresh tracks are advised to check the conditions on Avalanche Canada before leaving marked trails. The avalanche risk is currently rated at "Considerable" in the alpine area of slopes in the Sea to Sky region.

With files from CTV Vancouver's David Molko