Pipeline company TransCanada said about 400 barrels of oil leaked near the Keystone pipeline in South Dakota, far more than the company originally estimated.

The company started the process of closing down its Keystone oil pipeline after discovering oil released Saturday near a pump station in South Dakota. Initial estimates put the size of the release at about 125 barrels.

"We have completed our initial modeling and have provided to regulators an estimate of the potential volume of 400 barrels," the company said in an emailed statement.

The company maintained there were no threats from the release to the environment or to public health. A spokesperson said Monday the size of visible oil at the sight covered about 300 square feet. No response was offered when asked by UPI to address the revision to the size of the release.

The company said it based its estimate on the soil excavated to expose more than 100 feet of the pipeline. More than 100 workers were on site to assess the situation alongside members of the federal Pipeline and Hazardous Materials Administration.

TransCanada had a permit to build Keystone XL, an extension to the original pipeline, denied by the U.S. government in part on environmental grounds. Early critics of the project pointed to a history of breaks along the current route and raised concerns about the potential harmful environmental impact of heavy crude oil from Alberta.

The Keystone oil pipeline will remain closed while TransCanada examines the situation in South Dakota. The pipeline runs from Alberta, Canada, to terminals in Cushing, Okla., and Wood River, Ill. That section is directly impacted by the release, though consumers linked to a line stretching from Cushing to the U.S. Gulf Coast remain supplied.