A middle-aged man is dead and another is in hospital with serious injuries after a two-vehicle crash at Highway 7 and Weston Road in Woodbridge on Thursday morning.

Police asked motorists to avoid the area because the intersection was closed for several hours. It reopened at around 3:30 p.m.

York Regional Police said the collision involved a Honda Accord and a tractor-trailer unit shortly before 7:20 a.m.

Firefighters freed two people who were trapped in the car.

An air ambulance transported a male patient to St. Michael's Hospital in Toronto. That person suffered serious injuries, but his condition wasn't immediately available. Three other passengers were transported to hospital via ground ambulance with minor injuries. The driver of the tractor trailer was also taken to hospital with minor injuries.

The tractor-trailer unit, westbound on Highway 7, struck the passenger side of the car as it was making a left hand turn.

In addition to the intersection shutting down, Ontario Provincial Police also closed the northbound and southbound ramps from Highway 400 to Highway 7's westbound lanes.

The TTC said its 165 Weston Road bus is diverting around the scene.

A collision reconstruction unit and a forensic identification unit have been dispatched to the scene to investigate the cause of the crash.

Police are looking for witnesses.

"In an intersection as busy as this there are people out there that maybe saw the colour of the light or maybe saw or heard something else and we are encouraging them to come forward," Const. Rebecca Boyd of the York Regional Police told CP24.

Anyone with information is asked to call police at 1-866-876-5423 ext.7704.

With a report from CP24's Cam Woolley