CALGARY, Alberta - Enbridge Inc, Canada's largest pipeline company, was investigating on Sunday the cause of a 750-barrel spill of synthetic crude that forced it to shut three oil pipelines in northern Alberta.

The company said recent heavy rains in the region may have resulted in ground movements that affected the pipeline. It is working with regulators to assess the cause.

The rupture on Line 37 was spotted in the early hours of Saturday morning near Enbridge's Cheecham terminal, about 70 km (43 miles) southeast of Fort McMurray, Alberta. Enbridge declined to comment on the size of the 17-km (11-mile) pipeline that serves CNOOC Ltd's Long Lake oil sands project.

Enbridge said it had also shut down two other major oil pipelines serving Canada's oil sands region as a precaution while the company investigates the cause of the spill.

Shipment on the 345,000 barrels per day Athabasca pipeline, which carries dilbit blended crude to the Hardisty terminal in Alberta, and the Waupiso line, which can carry up to 600,000 bpd depending on crude viscosity, to Edmonton, Alberta, have been suspended.

"We anticipate restarting these lines as soon as we have confirmed their integrity through a geotechnical assessment, although it's too early to say when that will be," Enbridge spokesman Glen Whelan said in an email.

Further south in Alberta record-breaking floods caused widespread devastation. Three people died, more than 100,000 were forced to evacuate their homes and the centre of Canada's oil capital Calgary remained without power.

On Sunday, Enbridge said around 60 workers were on site, and the area had been secured and clean-up operations were underway. The release was contained within the Line 37's right of way, at a site with no major roads or human habitation nearby.

Mike Hudema, Climate and Energy Campaigner with Greenpeace Canada said the rupture was the latest in a chain of spills to hit Alberta.

"Once the flooding crisis has passed, we hope that the Alberta government will include a strategy for better preparing our pipeline system to deal with extreme weather events and will make the structural and regulatory changes needed so pipeline ruptures like this don't continue to plague our province," he said.