Commuters in the nation's capital will now face random bag inspections when using Washington, D.C.'s Metro transit system.
Washington started the indiscriminate carry-on searches Tuesday. Screeners swabbed and inspected bags in at least two Metro stations.
Similar efforts are already underway in New York and Boston.
Metro Transit Police Department Chief Michael Taborn said the program has been in the making for years and he hopes strengthen subway security.
Authorities said the searches are not in response to any particular threat.