THUNDER BAY, Ont. - Ontario's police watchdog has charged a provincial police officer following an alleged sexual assault that dates back more than 15 years.

The Special Investigations Unit says police contacted the agency in early February regarding a complaint they received against an OPP officer in Thunder Bay.

The SIU says the officer allegedly sexually assaulted a woman between April of 2001 and March of 2002.

The unit says 43-year-old Const. John Hayes is charged with one count of sexual assault.

The SIU is an arm's-length agency that is automatically called in to investigate incidents involving police where there has been death, serious injury or sexual assault.