There was a leak on Sunday at Sarnia's Imperial site.
On its Facebook page, the company posted there was an on-site release of a gasoline type product from a line.
The incident was discovered sometime Sunday afternoon.
Imperial said the leak was contained to company property and the emergency response team responded using foam and vacuum trucks.
According to the post, air monitoring at the fence line showed no readings.
The Ministry of Environment, Conservation and Parks was notified and a Chemical Valley Emergency Coordinating Organization (CVECO) information notice was issued.