A number of birds were covered in oil and ships were stranded in the St. Lawrence Seaway following a shipping accident that dumped up to 200 tonnes of fuel into the water.
The oil gushed from the punctured fuel tank of a ship that had an accident earlier this week.
Although the leak was quickly contained, about three kilometres of shoreline were affected by the slick and about 15 birds have been found covered in oil by the shore.
Nine ships were stuck in the seaway Wednesday and three more have had to drop anchor in the Port of Montreal.
The Coast Guard will determine when to reopen the waterway following Monday night's accident.
Canada Steamship Lines (CSL), which owns the ship, said in a release Wednesday it has contracted environmental specialists to "remove all traces of the spilled fuel from the shore and waters of the affected area."
"Additional booms will be installed along the shoreline of both sides of the river in order to contain and prevent further spreading of the oil," the company said.
Officials say mechanical problems caused the M/V Richelieu to run aground near Montreal's south shore. The ship, which had been carrying wheat, suffered engine failure during a heavy storm.
The accident occurred in a closed portion of the canal, limiting the amount of oil that flowed through the waterway.
Government experts said prevailing winds had pushed the water towards the shoreline, where it is easier to clean up oil. Water cannons were also used to help facilitate the effort.
CSL expects the cleanup to be finished by Tuesday.
In the meantime, the Richelieu will undergo repairs in order to continue its trip to Quebec City, where it will receive a more exhaustive overhaul after dropping off its cargo.
Authorities expect to have a better idea then about how much fuel actually spilled. The current estimate ranges from 50 to 200 tonnes .