A gunman dressed in all black fired shots on Monday inside the U.S. Navy Yard in Washington, injuring at least 10 people, CNN reported.
An official told CBS News that the number of victims could be higher because it is a "chaotic scene."
Media reports also suggested that three shooters, including one in military fatigues, were involved in the incident.
Police and emergency crews gathered outside the Naval Sea Systems Command Headquarters building, where the shooting was reported to have occured.
About 3,000 people work in the building.
People inside the building have been directed to stay in place, media reports said.
Naval Sea Systems Command is the largest of the Navy's five system commands.
It builds, buys and maintains the Navy's ships and submarines and their combat systems.
--IBNS (Posted on 17-09-2013)