Information from the Associated Press

Officials say a faulty weld at a bend in the Keystone oil pipeline contributed to the Dec. 7 oil spill in Washington County, that dumped nearly 13,000 barrels of crude oil into nearby Mill Creek.

Canadian-based TC Energy said Thursday the flawed weld caused a crack that then grew over time because of the stress on the bend which travels through rural pastureland. The company says the weld was for a fitting that connected two sections of pipe.

The company says it’s still investigating the cause of the pipeline stress and analyzing “other areas with potentially similar conditions.”

No one was evacuated following the spill, and officials say it did not affect the two nearby larger rivers nor Tuttle Creek Reservoir.

The spill was the largest onshore in nine years and larger than 22 previous spills on the Keystone system combined, according to U.S. Department of Transportation data.