Ontario Provincial Police say a woman is dead and two others are injured after a three-vehicle crash on Hwy. 401 early Saturday.
Police said they received a call around 1:15 a.m. for reports of a crash on the eastbound express lanes of Hwy. 401 near Islington.
OPP Sgt. Kerry Schmidt said it appears the chain-reaction crash occurred as traffic was slowing in the area.
Schmidt said one vehicle was unable to slow down in time and crashed into the back of another vehicle, which was travelling slowly.
The second vehicle was pushed and then collided with the back of a third vehicle that was nearly stopped.
Schmidt said three people were injured inside the first vehicle.
A 32-year-old woman who was sitting in the back seat of the car was the most seriously injured and was taken to hospital in life-threatening condition.
Police said she died on the way to the hospital.
Two other occupants in the vehicle, the driver and another passenger, were not seriously injured.
The highway was closed for part of the investigation but has since reopened.
Police are continuing to investigate and are looking into whether impaired driving, aggressive driving, mechanical failure or human error were factors in the crash.
Investigators are asking anyone who may have witnessed the crash to contact them.