A major catastrophe in the streets of College and Bay caused one woman to be seriously injured and the Toronto police sent two other women and a child to the hospital.
Toronto paramedics say three people taken to the hospital are pedestrians.
One other person was assessed on the spot, but was not taken to hospital, rescuers from Toronto added.
Pictures from the scene show a few people who look after someone on earth shortly after the catastrophe that took place around 15.20.
There are three damaged vehicles nearby.
Sergeant Brett Moore of Traffic Services said in a Twitter video that it looks like one driver "broke the light" by starting a chain of collisions. He said all drivers remained in place.
The police closed the intersection and the TTC service is being diverted. Authorities urge people to avoid this area during rush hour.
Investigators are looking for witnesses, although Moore said the incident was probably recorded on video. "There are cameras everywhere at the intersection," he said.
College and bay is closed due to a major accident. Several people to the hospital from the stage. Area closed to traffic ^ bm https://t.co/BAiTCOw4zc
It was a terrible week on the road in Toronto.
On Wednesday, a woman died after hitting a truck and then was hit by another driver. On Tuesday evening, the man died after hitting North York.