The collision happened before 4 a.m. and closed the QEW both directions from Seventh Street to Highway 406.
"It looks like one of tractor trailers actually went from the Fort Erie-bound QEW, flipped over the ramp into the Toronto bound [lane] and struck another tractor-trailer," said the OPP's Dave Woodford, describing the accident.
Shortly after the crash the OPP confirmed that one person died. At about 12:30 p.m. Thursday the OPP confirmed that a second person, the driver of one of the trucks, had died in hospital.
In a second accident, four people were taken to hospital with serious injuries following a crash on the eastbound Gardiner Expressway near Highway 427.
Police say a car was stalled in the passing lane just before 4 a.m. when it was struck from behind by another vehicle. Three people were trapped inside the stalled car.
The Toronto Fire Department removed the victims with the jaws of life.