At a Glance Originally, the pipeline owner estimated a 5,000-gallon spill.

The estimate now stands at 9,700 gallons.

The company says it has cleaned up the affected farmland.

A November 2017 Keystone pipeline oil spill in rural South Dakota was twice as large as originally believed, making it the seventh largest oil spill on U.S. soil since 2010.

Robyn Tysver, a spokesperson for pipeline owner and Calgary-based TransCanada, told the Aberdeen American News that the Nov. 16 leak near Amherst resulted in the release of some 9,770 barrels , or 410,340 million gallons, of crude oil onto farmland. Original estimates put the spill at 5,000 barrels, or 210,000 gallons.

When the leak was detected, the company shut down the pipeline that transports 590,000 barrels of oil a day from Canada's oil fields to refineries some 2,600 miles away in Illinois and Oklahoma, via the Dakotas, Nebraska, Kansas and Missouri. The pipeline was reopened less than two weeks later.

In the five months since the spill, the company says it has cleaned up the affected farmland.

"The remediation work on the property has been completed. We have replaced the last of the topsoil and have seeded the impacted area," Tysver told Aberdeen American News.

A final report on the incident by the federal Pipeline and Hazardous Materials Safety Administration is expected in the coming weeks. A preliminary report suggested that construction flaws in 2008 may have contributed to the leak.

The updated estimate has provided fodder for environmental groups that have been in a bitter fight to halt the Keystone XL pipeline project, which is an expansion of the existing Keystone pipeline that, if it goes through, will transport Canada's oil to the U.S. Gulf Coast.

Kelly Martin, director of the Sierra Club's Beyond Dirty Fuels Campaign, told weather.com the news is not surprising.

"On a pipeline that had a dozen spills in its first year of operation alone, it comes as no surprise that TransCanada failed to accurately estimate the size of this latest spill," Martin said. "This news is yet another reminder that TransCanada cannot be trusted to build their dirty tar sands pipelines through our land, water and communities. That's why we are continuing to fight to ensure that Keystone XL is never built."

In March, President Donald Trump issued a federal permit for the expansion project, countering a rejection of the project by the Obama administration.