Ontario Provincial Police have confirmed four people, including one child, were killed in a fiery, multi-vehicle crash Friday night on Highway 400 in north Toronto when a car drove into the back of a transport truck.

Paramedics had pronounced three adults and one child dead at the scene. Two people were taken to hospital with non-life-threatening injuries, while several others sustained minor injuries.

Paramedics initially reported five deaths, but police confirmed later four people were killed in the crash.

OPP confirm there were four fatalities in the collision on Highway 400 SB south of Finch Ave last night and one of the victims was a child —@OPP_HSD

The northbound lanes of the highway reopened around 8 a.m. Saturday, with the southbound lanes opening around 3:45 p.m.

OPP Sgt. Kerry Schmidt said the crash happened in the highway's southbound lanes shortly before 10 p.m. ET Friday night. A total of 12 vehicles, some of which sustained massive damage, were involved in the pileup.

Police say 12 vehicles were involved in the crash. (Mehrdad Nazarahari/CBC)

"These vehicles are completely unrecognizable," he said. "I think this is one of the most incredible scenes I've ever been to in terms of the number of fatalities and just the trauma that's been sustained and the way these vehicles ended up."

Schmidt said one of the truck trailers and several vehicles were gutted by a fire that was ignited by the crash.

The identities of those killed are being withheld pending notification of their next of kin.

(Canadian Press)

No word on cause

There was no early word on a possible cause for the horrific accident, though Schmidt noted the weather and road conditions were both good, and there was no highway construction underway at the crash site.

OPP's collision reconstruction team remained on the scene well into Saturday morning.