NEW: Both vehicles in a firey crash, were headed westbound on the 407

Ontario Provincial Police say they're investigating mechanical failure as a possible cause of yesterday's crash that killed two men on Highway 407.

Sergeant Kerry Schmidt says human factors are also still under consideration, but a vehicle malfunction on the fuel tanker involved in the crash is a leading possibility.

The tanker and a passenger vehicle were both destroyed in the crash that took place just before 5 p-m yesterday.

The drivers of both vehicles, a 41-year-old from Brampton, and a 49-year-old from Mississauga, died at the scene.

Schmidt had previously said the fuel truck was heading westbound when it jumped the median and collided with an eastbound passenger car.

But he says investigators have since determined both cars were heading westbound and that the passenger vehicle got caught when the truck swerved.

Highway 407 reopened early this morning after being closed for a little more than 12 hours.