The incident took place around 2 a.m., when police say a man in his 30s crashed his car on Earnscliffe Road and then fled the vehicle.
Police officers pursued the man into an Oakwood Avenue backyard, where the man collapsed shortly after being apprehended.
Paramedics performed CPR on the man, who was rushed to a nearby hospital.
Police haven't released an update on the man's condition, nor said how he sustained his injuries.
The SIU investigates all incidents involving police in which death or serious injury occur, or when allegations of sexual assault are raised.