The Ministry of Environment says the source of a gasoline leak in Kapuskasing was from a weeping tile connected to a nearby gas station.
Last Thursday, the community declared a state of emergency due to the leak, and about 100 families had to leave their homes.
The ministry said the weeping tile was connected directly to the city's sanitary sewer system. The municipality has plugged the weeping tile to prevent any further leaking of gasoline.
Ministry officials remain on site to determine how the fuel entered the weeping tile, and what the owner will need to do to ensure it doesn't happen again.
The evacuees have returned to their homes.