In Vaughan, a man died when his car crashed at Langstaff Road and Edgeley Boulevard, just east of Highway 400.
York Regional Police say no other cars or pedestrians were involved in the accident.
And the province's Special Investigations Unit has been called in after a single car accident in Port Hope.
The SIU says it appears Port Hope police officers tried to stop a vehicle just before midnight.
The car sped away and later left the road, struck a tree and rolled over.
The 30-year-old male driver died later in hospital.
The SIU is called in any time there are incidents involving police and the public where there has been death, serious injury or allegations of sexual assault.
No names have been released.