The accident between the bus and two cars occurred late during rush hour at an intersection in an industrial park in the municipality of Dorval, near the Montreal airport.
Two people were declared dead on the scene — a 61-year-old female passenger in a BMW, and the bus driver.
The driver's body was later retrieved from under the bus. Two other people were seriously injured and at least a half-dozen others were slightly hurt.
The accident occurred at 6 p.m. A multitude of ambulances rushed to the scene, along with about a dozen other emergency vehicles. The road was closed off.
Those with serious injuries were among those whisked away to hospital. Police originally reported about 12 minor injuries and revised that number downward later in the night.
The force of the crash flipped the bus over, onto the lawn of a commercial property.
Two smashed cars lay nearby. On one car, the impact of the crash was so severe that the engine block was pushed inside the vehicle.
"It was clearly a major impact,'' said Bob Lamle, spokesman for the city ambulance service.
"The vehicles have major frontal damage and the first car, the front end is almost cut off.''
There were about 14 people riding on the bus.