BISMARCK, N.D. — A fatigue crack in the Keystone Pipeline led to an oil spill in North Dakota earlier this year that released thousands of barrels of oil onto farmland, according to the pipeline operator.

In a quarterly report released Thursday, South Bow said initial findings show, “the failure resulted from a fatigue crack that originated along the pipe’s manufactured long-seam weld.” A fatigue crack is a crack that grows larger with changes in pressure over time, Pipeline Safety Trust Executive Director Bill Caram said.

A mechanical and metallurgical analysis found the pipe and welds met industry standards, the company said.

Spill-related costs total around $55 million, which the company said it expects to recover through insurance early next year. Through September, South Bow had received about $16 million in reimbursements from its insurance policies.

The U.S. Pipeline and Hazardous Materials Safety Administration ordered several corrective actions after the spill. The federal government shutdown delayed the release of a third-party “root cause analysis,” South Bow said.

It’s unclear when those findings will come. A South Bow spokesperson said PHMSA is leading that process and “out of respect for the process, we can’t speak for them.”

An estimated 3,500 barrels or 147,000 gallons of oil spilled in a field near Fort Ransom, a small town in a forested area with outdoor recreation and scenic views.