Federal investigators had no trouble smuggling bomb-making materials past ill-trained and poorly supervised guards at federal buildings, senators were told at a hearing Wednesday.

“This is the broadest indictment of a federal agency I have ever heard,” Sen. Joseph Lieberman, I-Conn., said at a Homeland Security Committee hearing on the performance of the Federal Protective Service, the office responsible for the safety of some 9,000 federal facilities. “This is really serious stuff.”

The committee, chaired by Lieberman, heard how Government Accountability Office investigators on 10 occasions carried the components for an improvised explosive device through checkpoints monitored by FPS guards. In all 10 cases the bomb-making materials went undetected.

Mark Goldstein, the GAO’s director for physical infrastructure issues, said the investigators proceeded to assemble the material — made up of a liquid explosive and a low-yield detonator — in restrooms and walked freely around the facilities with the IED in a briefcase.

He said that in some cases the bathrooms were locked but employees working in the buildings opened them up for the visitors.