Part of the Keystone 1 Pipeline in North Dakota was shut down after a leak of about 9,120 barrels of oil -- 383,040 gallons -- was discovered, TC Energy company said in a statement.
The oil leak was discovered just north of Edinburg, in the northeast part of the state, and affected about 2,500 square yards of land, the company said. A drop in pressure was detected on Tuesday, and the pipeline was immediately shut down, the company said.
The company is not sure how the leak started, but says an independent party is examining the pipeline.
'We are establishing air quality, water and wildlife monitoring and will continue monitoring throughout the response. There have been no reported injuries or impacted wildlife,' TC Energy said.
'The safety of the public and environment are our top priorities and we will continue to provide updates as they become available.'
The North Dakota Department of Environmental Quality said the spill impacted a wetland area. 'Personnel from the NDDEQ are at the site and will continue to monitor the investigation and remediation,' the department said in a news release.
The Indigenous Environmental Network, an environmental justice nonprofit group, responded to the spill with concern.
'This is exactly the kind of spill we are worried about when it comes to Keystone XL being built. It has never been if a pipeline breaks but rather when,' said Joye Braun, Indigenous Environmental Network frontline community organizer.
The organization criticized the company, saying that it hasn't done enough to secure the infrastructure of the pipeline.
The Keystone Pipeline system stretches more than 2,600 miles from Alberta, Canada, east into Manitoba and then south to Texas.
Keystone 1 refers to phase one of the Keystone Pipeline that starts in Alberta and runs through North Dakota, South Dakota, Nebraska, Kansas and Missouri to refineries in Illinois and Oklahoma. Phase one started operating in 2011.
The controversial Keystone XL pipeline would begin in Alberta and extend south to Steele City, Nebraska. The company says it hopes to start construction in 2020.
The pipelines have sparked months-long protests. In 2017, a spill exposed 210,000 gallons of oil in South Dakota. As many as 10,000 people participated during the peak of the demonstrations.