Police in Brampton on Friday morning were telling drivers to steer clear of the area of Clark Boulevard and Torbram Road.
Officers were investigating a deadly crash that saw a car collide with a tactor-trailer.
Authorities say the driver of the car, a female, was pronounced dead at the scene.
Clark was closed off between Torbram Road and Walker Drive as police collected evidence.
The crash happened near Clark Boulevard and Summerlea Road, at around 10:30am, in an area of Bramalea known for big rigs and heavy manufacturing.
Peel Regional Police say its too early to tell what went wrong and that closures on Clark Boulevard could last hours.
There is no word yet on whether charges might be coming.