Crews clean up Wednesday after a Petro-Canada refinery owned by Suncor Energy leaked oil and chemicals into the St. Lawrence River. ((Melissa Kent/CBC))

Crews wearing masks worked non-stop in Montreal on Wednesday to clean up diesel fuel that spilled into the St. Lawrence River from a Petro-Canada refinery belonging to Suncor Energy Inc.

Suncor Energy said the source of the leak was found and that about 35 barrels of low-sulphur diesel made it into the river.

There appears to have been a rupture on a pipe connecting the refinery to the dock. Suncor cut off the flow of diesel shortly after the leak was discovered, late Tuesday night.

The company also said most of the product was contained inside floating booms and the mixture of fuel and water was being recovered with the use of vacuum trucks.

"Our emergency response team was activated immediately – assisted by the Montreal fire department – and containment booms were immediately deployed into the river," said Suncor spokesman Michael Southern.

One estimate is that the slick covered about half a kilometre of shoreline.

Environmental group warns of potential disaster


Suncor Energy officials have installed booms in the water to stop oil and chemicals from spreading. ((Melissa Kent, CBC))

One environmental group said the spill is a reminder of just how dangerous the refinery can be for the St. Lawrence River ecosystem.

Cameron Fenton of Climate Justice Montreal said the Suncor plant could become an important component of Enbridge's proposed Trailbreaker pipeline, which would pump crude from Alberta's oil patch through Quebec.

"Suncor wants to bring tar sands bitumen to this refinery," Fenton said in a statement released Wednesday.

"I don't even want to imagine the potential disaster if the dirtiest oil on the planet reaches the St. Lawrence River."

The seaway is the joint responsibility of the federal and provincial governments.

Officials with Environment Quebec and Environment Canada are at the scene to ensure the cleanup operation follows guidelines.

Firefighters arrived on the scene at 8:30 p.m. Tuesday after people living in the area reported a strong smell of fuel.

The refinery is located at the corner of Marien Avenue and Notre-Dame Street East.

With files from The Canadian Press