CALGARY — The CEO of TC Energy Corp. says the company is cleaning up and investigating the cause after an "unfortunate" Keystone pipeline leak in North Dakota spilled an estimated 1.45 million litres of oil earlier this week.

North Dakota Gov. Doug Burgum has asked the company to review its inspection and monitoring in light of the spill, but Russ Girling defended TC Energy's spill response on a conference call Friday to discuss its third-quarter results.

"In this instance, our leak detection systems enabled us to remotely shut down the pipeline and our crews moved to the scene immediately," he said.

"Today, we are focused on cleaning up the site, determining the cause and returning the line to service."

The Republican governor spoke Thursday night to officials at the Calgary-based company formerly known as TransCanada Corp., said Burgum spokesman Mike Nowatzki.

The conversation came two days after the company shut down the pipeline after the leak was discovered.

Burgum said in a statement he "received assurance" from the company that the spill would be cleaned up "as thoroughly and quickly as possible."

On its website, TC Energy says the spill has affected about 2,000 square metres of land, or "less than half the size of a football field," and the estimated 9,120 barrels of oil were "approximately half the size of an Olympic-sized swimming pool."

North Dakota regulators said some wetlands were affected, but not any sources of drinking water.

The pipeline remained closed Friday and the cause of the spill was still unknown, said State Environmental Quality Chief Dave Glatt.

About 15,900 litres of crude oil have been recovered from the spill, Glatt said. Workers were expected to dig up a portion of the underground pipeline within the next few days to inspect it, he said.

"The company has the spill contained and nothing is moving offsite," Glatt said.

Crude began flowing through the $5.2-billion Keystone pipeline in 2011.

It's designed to carry crude oil across Saskatchewan and Manitoba, and through North Dakota, South Dakota, Nebraska, Kansas and Missouri on the way to refineries in Patoka, Ill. and Cushing, Okla.

The pipeline spill and shutdown come as the company seeks to build the US$8-billion Keystone XL pipeline that would carry oilsands oil from Alberta to refineries in Texas. The proposed pipeline has drawn opposition from people who fear it will harm the environment.

President Donald Trump issued a federal permit for the expansion project in 2017, after it had been rejected by the Obama administration.

TC Energy reported on Friday its net income slipped in the third quarter after it sold $3.4 billion in assets in the first nine months of the year.

The company said net income came in at $739 million for the quarter ending Sept. 30, compared with $928 million for the same quarter a year earlier.

Adjusted earnings, which exclude a variety of tax impacts from its asset sales, were $970 million or $1.04 per share, up from $902 million or $1.00 a year earlier.

Analysts had expected adjusted earnings of $922 million, or 98 cents per share, according to financial markets data firm Refinitiv.

TC Energy also announced a $1.2-billion expansion of its western Canadian gas-gathering system called the West Path Delivery Program, which is to connect with the US$335-million GTN XPress Project recently announced by its U.S. limited partnership, TC PipeLines LP, to deliver the volumes to downstream markets.

It said the West Path project is underpinned by about 260 million cubic feet per day of new firm service contracts with terms that exceed 30 years, starting in late 2022.

-- With files from the Associated Press