"CALGARY, Alberta/WASHINGTON - 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.

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."

Nia Williams and Valerie Volcovici report for Reuters December 4, 2017. [2]