The Special Investigations Unit (SIU) is investigating a complaint involving a Sarnia police officer.
City police said an allegation was received June 4, that an officer had sexually assaulted a member of the public.
Due to the nature of the complaint, the SIU was notified the same day and the SIU advised the police service it would be invoking its mandate June 16.
The SIU is an arm's length agency that investigates reports involving police where there has been death, serious injury, or allegations of sexual assault.