Police said in an early morning news release they were investigating after they found "two male occupants in the vehicle that are deceased. We have no identity, ages or where they are from at this time."
A passerby saw the car on a secluded road and contacted police at about 6:15 a.m.
The passerby said he detected a foul odour coming from the car. Police later said "notes were posted inside and around the vehicle warning of dangerous gas and to call 911."
Police, firefighters and EMS workers are all at the scene at 15th Side Road, near Weston Road.
The road is a dead end with very little traffic.
According to the release, "King and Vaughan Fire are currently taking every precaution as we do not know what we are dealing with in terms of dangerous gasses or chemicals."
Police have not released any information on the identities of the males.