Workers continue their efforts on exposed sections of the Keystone pipeline. An estimated 210,000 gallons of oil leaked from the Keystone Pipeline in Marshall County, South Dakota, according to the pipeline's operator, TransCanada. Crews shut down the pipeline and officials are investigating the cause of the leak. A federal agency says a leak was caused by damage during construction in 2008. The Pipeline and Hazardous Materials Safety Administration issued a corrective action report 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.