TransCanada Corp said on Monday a part of its Keystone crude pipeline from Steele City, Nebraska, to Patoka, Illinois, remained shut after a leak was discovered in the St. Louis, Missouri, area last week.
The cause and source of the spill have not been determined and there is no estimated timeline for a restart, TransCanada spokesman Terry Cunha said in an email.
The 590,000 barrels-per-day Keystone pipeline system is a critical artery taking Canadian crude from northern Alberta to U.S. refineries.
TransCanada told Keystone shippers last week that it was declaring force majeure on shipments affected by the shutdown, according to a notice seen by Reuters. Force majeure is a declaration that unforeseeable circumstances prevented a party from fulfilling a contract.
Canadian pipelines have been running at capacity as a production surge in Alberta overwhelmed existing pipeline infrastructure, forcing the Alberta provincial government to order production cuts starting last month.
Canadian heavy crude has in recent days attracted greater demand following U.S. sanctions against Venezuela's state oil company.
The discount on Canadian heavy crude compared with U.S. light oil was at about $11.50 per barrel on Monday, steady from Friday's settlement, according to Net Energy Exchange.
Missouri's Department of Natural Resources did not immediately respond to a request for comment on Monday.
(Reporting by Devika Krishna Kumar in New York Editing by Paul Simao and Dan Grebler)