Three people have died and more than a dozen others have been injured in a multi-vehicle crash on a major highway east of Toronto.

"It is a huge scene here," Ontario Provincial Police Sgt. Kerry Schmidt said Saturday morning of the collision Friday night on Highway 401 at Whitby, Ont.

A man, a woman and a boy died in the pileup, Schmidt said, adding that as many as 20 vehicles, including four tractor-trailer trucks, were involved in the collision in the westbound lanes of the highway.

"With all these vehicles crumpled up, it's an unbelievable scene here with steel and aluminum twisted around from these vehicles that are not even recognizable as cars," he said.

"Five of the injured were in critical condition with life-threatening injuries and that another 11 suffered serious injuries and had been take to hospitals across the region, Schmidt said.

Schmidt said the collision occurred at a construction zone.

"It appears that one of the transport trucks was travelling westbound and as traffic began to slow in front of it due to construction this vehicle did not slow down and continued right into the back of traffic," he said.

Schmidt said the road was dry, there were no environmental conditions and visibility was good at the time of the crash.

The highway, which is among Canada's busiest, was closed in both directions at the accident site so equipment could be brought in to remove the damaged vehicles from the scene.

Schmidt said he expected the westbound lanes would remain closed into Saturday afternoon and no charges had been laid as of Saturday morning