TransCanada Corp.is investigating a leak that shut its Keystone oil pipeline in South Dakota.

The leak occurred about 4 miles from the Freeman pump stationin Hutchinson County, TransCanada told local media in a statement. The news releasewas on its media website, and company representatives did not immediately respondto emails seeking comment.

TransCanada anticipates restarting the conduit between the oilsands region of Alberta and U.S. hubs by April 8, according to a report by CNN Money.The company reported a spill of about 187 gallons to the U.S. Coast Guard's NationalResponse Center on April 2, CNN reported.

"We had a report of substance that was on this field behindus here and it's being investigated, we're trying to determine what's happened,"TransCanada spokesman Shawn Howard told TheDaily Republic of Mitchell, S.D., in avideo interview. "We're responding to something that's happened on our Keystonesystem, and it's going to take a little time to figure that out."

The incident was first reported on the afternoon of April 2,and the Calgary, Alberta-based company immediately shut the line, reports said.Emergency crews dispatched to the area found visible signs of oil over a small surfacearea. TransCanada said regulatory agencies and landowners affected by the incidenthave been notified.

A photo on TransCanada's official Twitter feed show a sectionof a ditch adjacent to a rural road marked off with yellow tape. A second photoshows an excavator moving soil from a field.

The Keystone network, which would have included the C$8 billion Keystone XL line,can carry as much as 590,000 barrels per day from Hardisty, Alberta, to refineriesin Illinois and storage facilities in Cushing, Okla. A southern leg can carry asmuch as 700,000 bbl/d from Cushing to the Houston area. The U.S. Department of Statein 2015 denied a needed permit for Keystone XL, which would have carried oil sandscrude across a more direct route and boosted the network's capacity. Environmentalgroups, including the Natural Resources Defense Council, supported the cancellationof the project.

"This weekend's Keystone oil spill is the latest stark reminderthat all too often with pipelines it's not whether they will leak but when,"the group's Canada program director, Anthony Swift, said in a statement. "Thisspill clearly reinforces the need for the Obama administration to require a thoroughenvironmental review for [EnbridgeInc.]'s Alberta Clipper and other efforts to expand its Midwestern tarsands pipeline system. And that review should put protecting the public from oilinfrastructure harm as the highest priority."