Police shut down a section of Canada's busiest highway Tuesday after a body was dumped from a moving car in northwest Toronto.

Police Constable Tony Vella said it appeared the victim was shot and then pushed from a Lexus into the eastbound lanes of Highway 401. He said police were hunting for the car.

Yellow police tape stretched across three lanes of the highway near an exit and police erected a blue tent over the body to preserve evidence.

Vella said police were investigating a report that the suspected shooter was female, and were interviewing several witnesses.

The investigation forced traffic to a standstill, with cars backed up for miles. Traffic was also slow in the eastbound express lanes as drivers slowed to look.

More than two dozen emergency vehicles, including police cruisers, fire trucks and ambulances, responded.

Police would not confirm whether a burned vehicle found abandoned near a golf course was connected to the case, or whether there was a possible connection to a fatal shooting near a bus stop in the city's northwest end on Monday.

Vella would only say that police were investigating all leads.