Police have re-opened all southbound lanes of Highway 404 near Finch Avenue following a multi-vehicle crash involving a pickup truck.
The chain-reaction accident, which happened at about 11 a.m., involved two minivans, a car and a pickup truck hauling a flatbed trailer, OPP Const. Dave Woodford told the Toronto Star.
"One vehicle stopped and there was heavy traffic at the time, and another one went into the rear end and another," Woodford said from the crash scene.
"It was definitely not caused by weather conditions. The roads aren't icy up here."
Five people were injured in the incident, with the most serious being a passenger in a car that was trapped and had to be extricated.
She was airlifted to Sunnybrook Hospital. None of the victims are believed to have suffered life-threatening injuries, police said.
Traffic in both directions was backed up for hours as the northbound lanes were temporarily closed to allow an air ambulance to land on the roadway.
Motorists were being diverted off the busy highway at Finch, which caused gridlock on nearby roads.
Police are investigating the accident. It is still not clear what triggered it.
With a report from CTV's Jim Junkin
