Waterloo Regional Police are investigating the sexual assault of a man on a trail west of the Chicopee Tube Park around 11:30 p.m. Monday night.

Police say the victim told them he was approached and grabbed from behind and sexually assaulted by an unknown male on River Road in Kitchener.

The victim described the suspect as being large with a heavy build.

Investigators with the police's Special Victims Branch and the Major Crime Branch are investigating the incident.