The Department of Transportation is under fire from Democratic lawmakers as they press the agency for answers about the Amtrak train that derailed in Washington last month, which took the lives of three passengers and injured many more.

In question is whether the department has been fully implementing a provision of the Fixing America’s Surface Transportation Act that instructs passenger railroads to locate high-hazard curves on the train tracks, and then file an action plan to the DOT to boost safety in those hazardous areas.