The province’s police watchdog has launched an investigation into a man’s death after he collapsed while in the custody of Toronto police.The Special Investigations Unit (SIU) said a Toronto police officer attended a scene on Sunday at around 4 p.m. near Liberty Village, in the area of Dufferin Street and Springhurst Avenue, alleging a man had driven his vehicle through a road closure at the intersection.The 64-year-old man was taken to a police station, and while in the booking process, the SIU said the man collapsed. He was transported to a hospital for treatment and was pronounced dead just after 6 p.m.No other details were provided. Two investigators and one forensic investigator have been assigned to the case, the SIU said.The SIU is an independent government agency that investigates the conduct of officials that may have resulted in death, serious injury, sexual assault and/or the discharge of a firearm at a person.