Oil from Canada Steamship Lines freighter which spilled in the St. Lawrence Seaway near the South Shore municipality of Sainte-Catherine Monday night has been contained.

Clean-up measures began Tuesday, though officials say they unclear how much oil escaped the freighter. Estimates run anywhere from one to 20 tonnes.

The incident occurred after the crew of the vessel dropped its anchor Monday after running into mechanical problems. At 7:30 p.m., high winds pushed the ship, and the fuel tank was punctured when it ran aground, spilling oil into the river near a lock in the South Shore canal system.

"As the tank was punctured at the bottom, water rushed into the tanks – as opposed to oil leaking out – so the water pushed the oil to the top of the tank," explained Claude Dumais, of Canadian Steamship Lines.

Crews installed booms in the water in an attempt to control the spill, but could not stop oil from flooding the desk and leaking over the side, washing up along three kilometres of coastline.

The vessel's fuel tank has a capacity of 50,000 litres, but officials don't know how much oil spilled. All they can say is that diesel fuel was remaining in the tank when the leak was patched about 2 a.m. Tuesday.

"Over the last 50 years we've never had a spill similar to this," said Jack Meloche of the St. Lawrence Seaway. "For us it's unique at this point, which is why all our partners are here, and we're working the best we can."

Officials are asking curious onlookers to avoid the site.

"We ask that people not going near the river because there's a lot of oil," said Yvan Leroux of Quebec civil security.

Environmental concerns

The municipalities of Candiac and La Prairie have been advised to monitor their water filtration plants to ensure the fuel does not make it into drinking water, though fears were quelled, because the water intake derives from the middle of the St. Lawrence River, which is protected by a levee and separated from the Seaway.

"(The plants) were informed by communiqué that their citizens did not have to be afraid whatsoever," said Candiac Mayor Andre J. Cote.

The advisory is purely a cautionary measure, said Christian Blanchette of Environment Quebec.

"Nothing has touched to those installations for now, and they're still monitoring," said Blanchette. The spill is "mostly confined on the Seaway shore."

Precautions are still being made, said Luc Brault from the plant.

"(Overnight) the supervisor in charge of the water filtration plant verified every hour for smell, and this morning he told me he never smelled any fuel," said Brault.

There have been reports that some birds have landed in the slick, and ended up covered in oil, but as of the noon hour nobody from Environment Canada had spotted any affected animals.

Anyone who has seen wildlife affected by the spill should call Environment Canada at 514-283-2333 or 1-866-283-2333.

The patch was visible Tuesday throughout the Seaway between Ste. Catherine and Kahnawake. While floating barriers were erected to stop the fuel, it reached surrounding shores.

"We will do the clean-up on the water, (but) I think we have to stop the oil going on the shoreline," said Sonia Laforest from Environment Canada.

Kahnawake Council Chief Clinton Phillips, who is responsible for environmental issues on the Mohawk reserve, said he doesn't feel reassured.

"Our environment office and our community protection (group) are working together, watching this closely and working with Environment Canada to see what's going on, because we're getting conflicting reports," said Phillips.

River-going traffic stopped

Traffic through the Seaway has been stopped while authorities try to clean up the fuel sitting on top of the water. Currently four vessels are waiting for permission to use the locks.

"At this point, it's not a major concern, but it is a concern. So right now, the seaway remains closed until everything is fixed up," said Meloche.

Canada Steamship Lines, the largest shipping company in the nation, was acquired by Former Prime Minister Paul Martin in 1981. He transferred management of the firm to his son in 2003.