The Keystone XL pipeline is expected to be a major contributor to U.S. crude oil production this year.
But in recent weeks, two pipelines have leaked, threatening the pipeline’s future.
Keystone is the only major oil pipeline in North America that carries crude from Canada to refineries on the Gulf Coast.
It is one of two major pipelines under construction to carry oil from the tar sands of Alberta, Canada to markets in the United States.
A third pipeline is in the planning stages.
The pipeline is about 880 miles long and would carry 2.6 million barrels of crude per day.
The leaked Keystone pipeline, which carries oil from Alberta’s tar sands, was discovered last year.
It leaked last week, according to officials from the Federal Energy Regulatory Commission, and has since been closed to traffic.
The pipeline was built by the Canadian firm Enbridge Inc., and the leak prompted the cancellation of the second phase of construction, according a statement from the commission.
The agency has not released the location of the leak, but Enbridge told the Associated Press that it has “implemented an emergency response plan to protect the pipeline system and prevent a further incident.”
“Enbridge is working with the company to investigate the cause of the pipeline leak and is providing an update on the status of the emergency response efforts,” the statement said.
The leak came about when Enbridge and the U.K. company First Energy failed to pay contractors for their work, the company said.