The Ontario Provincial Police (OPP) are investigating the cause of a large oil spill on Highway 401 near Chatham.
At around 10 a.m. on Saturday, police received a report of a single-vehicle collision on the road.
While investigating, the OPP determined that an unknown vehicle had previously spilled a substantial amount of oil on the highway.
The westbound lanes between Bloomfield Road and Queens Line were closed for several hours but have since reopened.
Anyone with information on the oil spill is asked to contact OPP at 1-888-310-1122 or Crime Stoppers at 1-800-222-8477 (TIPS).