Police say that at about 11:54 p.m., a dark-coloured van was stopped at a red light at Ontario Boulevard and the south side of Lakeshore Boulevard West. As the driver waited at the light, two women approached the van from behind and climbed onto the rear bumper. One of the women either tried to get off, or fell off.
The driver continued westbound on Lakeshore Boulevard West.
The woman was taken to hospital for treatment.
Police say the vehicle looks similar to a Mercedes-Benz Sprinter van. They say the driver may have been attending or working at an event called the Full Flex Express, which was held at TD Echo Beach on Saturday.
They're asking anyone with information to contact police at 416-808-1900 or Crime Stoppers at 416-222-TIPS (8477), or online at www.222tips.com.