Three people were killed in a massive avalanche which occurred Saturday afternoon in western Canada's British Columbia.

A dozen were injured, some in critical conditions. With many more unaccounted for, a large-scale search and rescue operation has been underway in Boulder Mountain, near southeastern BC's Revelstoke, Canadian Broadcasting Corporation said.

It's not clear how many people were missing, but the slide happened when hundreds were attending an annual snowmobiling event. There were reports that 20 to 30 people could be missing.

According to the Canadian Avalanche Centre (CAC), the area has been struck by 10 avalanches since Friday when CAC issued an extreme avalanche warning for the area.

Revelstoke is located within the Columbia Mountains in the Interior of BC, 641 km east of Vancouver.