Police are investigating a pair of overnight crashes, including a fatal collision on the Queen Elizabeth Way near St. Catharines, CP24 and 680News report.
One person is dead and three others are in hospital with life-threatening injuries after a tractor-trailer collided with a car at Highway 406.
Ontario Provincial Police say the QEW is closed in both directions at the crash site and is expected to remain closed for most of the day.
In the second incident, four people were taken to hospital with serious injuries following a crash on the eastbound Gardiner Expressway in west-end Toronto.
Police say a car was stalled in the passing lane near Highway 427 just before 4 a.m. when it was struck from behind by the other vehicle.
All Toronto-bound lanes are expected to re-open shortly.