Crews have been working to stem a leak of thousands of barrels of oil from the Keystone Pipeline into a creek in Washington County, Kansas, that prompted the shutdown of the entire Keystone system.The pipeline’s operator, TC Energy, said it detected the spill along Mill Creek on Wednesday, December 7. On Thursday, it said crews had isolated the affected segment of the pipeline.The Environmental Protection Agency (EPA) said several of its “on-scene coordinators” were also at the site, working with TC Energy employees and providing oversight of containment and cleanup operations.The EPA on Saturday said TC Energy had erected an “underflow dam” to prevent further movement of the oil.These satellite images, which Maxar Technologies said were captured on Saturday, show affected parts of Mill Creek. Credit: Maxar via Storyful