A U.S. regulator’s preliminary investigation into the biggest oil pipeline spill this year has raised a red flag that could trigger an extensive and costly inspection of tens of thousands of miles of underground energy lines. An aerial view shows the darkened ground of an oil spill which shut down the Keystone pipeline between Canada and the United States, located in an agricultural area near Amherst, South Dakota. REUTERS/Dronebase The 5,000-barrel leak on TransCanada Corp’s ( TRP.TO ) Keystone pipeline on Nov. 16 in South Dakota might have stemmed from damage caused by a weight put in place when it was built in 2008, the Pipeline and Hazardous Materials Safety Administration said in a report published on Tuesday. Weights are used to prevent pipelines from moving and reduce the risk of damage or ruptures when water tables rise. Sponsored The regulator’s finding has implications for […]