Friday, US officials plugged a Keystone pipeline breach that spilled up to 588,000 gallons of petroleum into a creek.
The Pipeline Safety Trust, which advocates pipeline safety, estimates the spill will be the greatest US crude oil spill since 2013.
The pipeline operator, Canadian-based TC Energy, discovered the breach Wednesday night in Kansas and stopped oil flow.
"The impacted part of the Keystone Pipeline System remains isolated" and "spillage downstream is contained," the firm stated Friday.
On Friday, the Environmental Protection Agency was still investigating the discharge's cause.
Transportation Secretary Pete Buttigieg tweeted that officials "are monitoring and investigating the... leak."
The Pipeline and Hazardous Materials Safety Agency ordered the business to "take appropriate remedial procedures to protect" against harm from the 36-inch pipeline rupture.
TC Energy used vacuum trucks, oil skimmers, and an earthen dam four miles downstream from the burst location on Mill Creek, according to the EPA.
The EPA stated spill cleanup "will stretch into the following week."
Alberta oil flows through the Keystone Pipeline to various US destinations. It normally moves 600,000 barrels per day.
At 19:00 GMT on Friday, the business stated it was still evaluating service reinstatement. Reactivation requires PHMSA approval.
After the spill, oil prices jumped Thursday then plummeted again.