Federal regulators have ordered the operator of the Keystone Pipeline to take several corrective actions after a rupture earlier this week caused more than 556,000 litres of oil to spill onto farmland in North Dakota.

The pipeline operator, Calgary-based South Bow, said its goal is to resume deliveries to refineries in the next few days. 

The Pipeline and Hazardous Materials Safety Administration (PHMSA) directed South Bow to submit the failed section of pipe to a third-party lab for mechanical and metallurgical testing, the agency said in a statement Friday.

The company must also conduct and submit a root cause analysis of Tuesday's failure and review all in-line inspection reports from the past 10 years to identify anomalies that may be present in the failed pipe, adjacent joints or anywhere else on the system, the agency added.

"PHMSA has already secured the operator's full co-operation and written commitment to take any steps necessary to repair the line and identify the cause of the failure," acting administrator Ben Kochman said in the statement. "Multiple PHMSA investigators are on the ground in North Dakota and in the operator's control room facility in Calgary working to determine the cause of the accident."

The order also requires an evaluation of the pipeline's special permit, which allows the line to operate at higher-than-normal pressures, to determine if new or modified conditions are necessary.

South Bow is still investigating the cause of the spill along the Keystone Pipeline near Fort Ransom, ND, about 100  kilometres southwest of Fargo. The spill from the underground pipeline released an estimated 3,500 barrels — or 556,455 litres — of crude oil onto farmland. 

The affected pipeline segment cannot be restarted until the U.S. agency gives the operator permission. South Bow said Saturday that it's aiming to restore service and energy deliveries by Tuesday as it carries out the order.

South Bow also said its response and recovery efforts were continuing. The company said its crews were preparing to repair and replace the affected section of pipe. It also said crews were onsite with vacuum trucks and other cleanup equipment, and that the work would continue over the weekend, too.

The company also said it would restrict operating pressures on the Canadian sections of Keystone, as agreed to with Canadian energy regulators.

The pipeline stretches 4,327 kilometres from Alberta to refineries in Illinois, Oklahoma and Texas. The spill has raised concerns about the impacts of a prolonged shutdown on energy prices, particularly for gasoline and diesel.

"Our primary focus remains on the safety of onsite personnel and mitigating risk to the environment," South Bow said. "We are committed to the community surrounding Fort Ransom and will continue clean-up activities until the site is fully remediated."