Mounties say the crash happened Monday night on Highway 63 north of Atmore, about 200 kilometres northeast of Edmonton, closing the road in both directions.
Police say a southbound semi appeared to have lost control while braking and crossed into oncoming traffic, colliding with two northbound cars.
RCMP say the driver in the first car had serious, but not life-threatening injuries, while there were four people in the second car, which burst into flames.
Mounties say nearby construction workers helped get the people out of the burning vehicle before it was totally engulfed in flames.
Three people were flown to Edmonton hospitals via STARS and fixed wing aircraft, while the others went to area hospitals.
Also on HuffPost