AMHERST, S.D. — A federal agency says a leak in TransCanada Corp.’s Keystone oil pipeline in South Dakota likely was caused by damage during construction in 2008.

The Pipeline and Hazardous Materials Safety Administration issued a corrective action report Tuesday on the estimated 210,000-gallon oil spill. The report says a weight installed on the pipeline nearly a decade ago may have damaged the pipeline and coating.

According to the report, weights are placed on the pipeline in areas “where water could potentially result in buoyancy concerns.”

TransCanada spokesman Mark Cooper said the company has been working cooperatively with the federal agency and has begun “a safe, controlled and gradual startup” of the pipeline. Cooper says that process will continue over the next couple of days.

South Dakota officials don’t believe the leak polluted any surface water bodies or drinking water systems. The company disclosed the buried pipeline leak on agricultural land in Marshall County on Nov. 16.