They say several people have been taken to hospital with non-life-threatening injuries, adding most of the occupants of the vehicles escaped injury.
RCMP say the area of the collision was experiencing thick smoke and foggy conditions at the time and visibility was greatly reduced.
Fire departments and EMS crews from Smoky Lake, Vilna and Waskatenau responded to the incident.
RCMP say there were frightening moments for rescue crews working at the initial collision, which involved seven vehicles.
Mounties say three vehicles including a rescue vehicle were knocked into the crash scene by a fourth vehicle approaching from behind.
The highway was closed to traffic for several hours to allow for crews to clear up the debris, but has since reopened.
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