By CBS News, July 3, 2015

As Americans celebrate the country's 239th birthday, law enforcement officers remain on high alert following an increased threat of a terror attack.

Sources tell CBS News that special Transportation Security Administration (TSA) teams are being assigned to large airline hubs and investigators are watching potential suspects.

Moments after a suspected gunshot was reported at the Washington Navy Yard, hundreds of officers from upwards of a dozen local and federal agencies descended on the area amid heightened concerns of a terror attack.