Suncor responded to an incident on the St. Clair River on Wednesday night.
An alert was issued just after 7:30 p.m., after the Suncor Sarnia Refinery identified a hydrocarbon sheen on the river.
The notification added the outlet of the release has been identified and contained.
Suncor said response equipment including booms and vacuum equipment were immediately deployed and clean up is underway with support from Eastern Canada Response Corporation.
Community members may notice increased activity in the area of the Suncor dock and associated odours are also possible.
The company said all appropriate regulatory agencies and local community organizations have been notified.
St. Clair Township said the municipal water system has not been affected by the spill.
