Ontario's police watchdog is investigating the circumstances around an arrest in Etobicoke that resulted in a 42-year-old man being sent to hospital with a serious injury.

The Special Investigations Unit (SIU) says Toronto police were sent an Etobicoke address early Sunday, after receiving a call about a sexual assault sometime after midnight.

Police located the man just before 2:00 a.m. near Lakeshore Boulevard and Twenty Ninth Street and arrested him. After that, the man was taken to hospital.

The SIU is asking that anyone who witnessed the incident to contact its lead investigator at 1-800-787-8529.

The agency is called to investigate reports of death, serious injury or allegations of sexual assault involving police.