Parks Canada spokesman Mark Merchant says mud, rock and large trees poured onto the highway late Friday night near the spot where the road overlooks the Spiral Tunnels on the Canadian Pacific Railway.
Merchant says no one was injured, but provincial officials in B.C. say the highway will likely remain closed until Sunday afternoon.
He says the slide likely occurred because the area has received a lot of rain lately.
Traffic is being detoured south on Highway 93, which has reopened after being closed Friday due to a fatal crash that involved a fuel tanker.