A TransCanada Keystone Pipeline pump station operates outside Steele City, Nebraska March 10, 2014.
A part of TransCanada's Keystone oil pipeline, the crucial route carrying crude oil from Canada's Alberta province to US refineries, has been shut down for investigation of a possible leak near St. Louis in Missouri, a TransCanada spokesman told Reuters on Thursday.
TransCanada spokesman Terry Cunha said in a statement that the Keystone pipeline was closed from Steele City, Neb., to Patoka, Ill.
The shutdown of part of Keystone comes at a time in which Canadian heavy crude is becoming increasingly in demand as refiners look to replace the heavy crude grades from Venezuela after the US slapped sweeping sanctions on the Latin American country's oil industry and its state oil firm PDVSA.More news: Thai King Dashes Sister's Political Dreams
Canadian pipelines are congested because of expanding production in recent years, forcing the Alberta provincial government to order production cuts starting last month.
The disruption comes as refiners seek alternative supplies of heavy crude on the U.S. Gulf Coast after sanctions on Venezuela effectively cut access to the country's oil.
On Thursday, TransCanada said it would cut the global joint spot rate on the Keystone line from Hardisty, Alberta, to Port Arthur and Houston by about $1 a barrel, according to a Federal Energy Regulatory Commission filing.
The discount on Canadian heavy crude compared to USA light oil widened to $10.50 United States per barrel on Thursday morning from $9.40 earlier, according to Net Energy Exchange.More news: Delta, Coke blasted over ‘creepy’ new napkins
The leak volume is estimated at 43 barrels of crude oil on land, according to Missouri's Department of Natural Resources.
Keystone runs parallel to Enbridge's Platte line and feeds refineries owned by BP Plc, Marathon Petroleum Corp and one jointly by Phillips 66 and Cenovus Energy.
Enbridge did not immediately respond to a request for comment.
TransCanada shares eased 0.7 per cent to $55.71 Cdn in Toronto while Enbridge shares slipped 1 per cent to $48.88 Cdn.More news: Rising conservative activist Candace Owens criticized over Hitler comments
Missouri Department of Natural Resources spokesman Brian Quinn said in an email that if Keystone is confirmed to be the source, "it will remain closed until the cause is determined and necessary repairs or corrections can be made and verified".