A fatigue crack was the probable cause of a 2017 pipeline rupture in South Dakota that spilled thousands of gallons of crude oil, according to a pipeline accident brief released by the National Transportation Safety Board (NTSB).

The TransCanada Corporation, Keystone Pipeline ruptured near Amherst Nov. 16. Keystone’s Supervisory Control and Data Acquisition system detected the leak but approximately 5,000 barrels of crude oil were spilled before Keystone’s Operational Control Center in Calgary, Alberta, shut down the pipeline. There were no injuries or fatalities associated with the incident.