The incident occurred in mountainous terrain at the Jasper National Park in the province of Alberta, public broadcaster CBC reported.
Several others sustained serious injuries and were flown to nearby hospitals on helicopters from the Shock Trauma Air Rescue Service (STARS) air ambulance, CBC reported. Ambulance, park administrators, and police have been dispatched to the scene.
"Saddened to hear of this accident in the Icefields. Thanks to @STARSambulance, EMS [Emergency Medical Services], front-line health workers, and Parks Canada staff for their quick action and care in responding", Alberta Premier Jason Kenney wrote on Twitter.
The bus was carrying 27 passengers and was specially modified to traverse icy surfaces and glaciers. The circumstances of the incident are being investigated, the broadcaster reported.