(Calgary) TC Energy said Friday that a third-party investigation into an oil spill from its Keystone pipeline in December concluded that the incident was caused by a crack in a weld made during the pipeline construction.

The Calgary-based company claims that the affected pipe segment was subjected during construction to “unintended bending stresses”, which caused a small crack that progressed over time until the pipe failed. after a decade of operation.

TC Energy says the results are consistent with the findings of an earlier metallurgical analysis, the results of which were released by the company in February.

A US regulator had ordered TC Energy to assign a third-party investigation after the Keystone pipeline leaked about 13,000 barrels of oil in Washington County, Kansas in December.

The Canadian company is still on hand to clean up the mess. It claims to have recovered 98% of the spilled oil and remediated 90% of the banks of the affected creek.

Last month, the U.S. Pipelines and Hazardous Materials Administration expressed concern about the risk of additional spills from Keystone and ordered TC Energy to operate the pipeline at reduced pressure until it receives written permission from the regulatory body.