Enbridge also shut other pipelines in the area as a precaution, including the Athabasca and Waupisoo pipelines.
The release of crude comes as Alberta grapples with major flooding, including in the city of Calgary where Enbridge has its head office.
Enbridge said in its initial assessment that unusually heavy rains may have resulted in a ground movement that affected the pipeline, which is part of its Athabasca network.
The company shut down Line 37 after a spill was discovered early Saturday near its Cheecham Terminal, about 70 kilometres southeast of Fort McMurray, Alta., which is the hub of Alberta’s oilsands industry.
The Alberta Energy Regulator said late Sunday that it was working on the problem but hadn’t confirmed the company’s estimate that between 500 and 750 barrels of oil had spilled.
The AES said Enbridge had installed wildlife deterrents and contracted environmental consultants to conduct water sampling and a wildlife survey.
It said there had been no impact on wildlife observed as of Sunday.