Thirteen people have been killed, including one gunman, in a shooting at a US Navy base in Washington.
Washington police chief Cathy Lanier said the motive for the shooting was unknown.
Authorities spent much of the day searching for two other potential suspects, before deciding that at least one of the two men was “not a suspect or person of interest,” according to a police statement released on Twitter
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Ms Lanier said people were being told to stay in their homes and out of the area as authorities search for the suspects.
Three federal law enforcement sources have tentatively identified the dead gunman as Aaron Alexis (34), a one-time Texas resident.
So far officials say there is no known link to terrorism.
Three of those wounded in the attack are in a critical condition but were alert and able to respond to doctors, a hospital official said.
President Barack Obama said the United States is facing “yet another mass shooting” and vowed to hold accountable whoever was responsible.
With details still emerging about the shootings at the Navy Yard, Mr Obama said he had been briefed on the situation and that the shooting had targeted military and civilian personnel. He spoke at the start of a speech about the US economy
Earlier amid confused sightings of possibly one, two or three gunmen, the Washington Post newspaper said two gunmen, including at least one in military clothing, were involved in the attack at the US Navy Yard base on the Potomac River.
Two witnesses told CNN affiliate station WJLA that they heard a fire alarm go off in the building where they worked, then saw a man with a rifle down the hallway as they exited the building.
“He aimed the gun and fired our way,” said Todd Brundidge said, adding, “I couldn’t believe it.”
People frantically tried to run out of the building, Mr Brundidge said.
“Everyone was going down the stairs. They were pushing. They were shoving. People were falling down,” he told WJLA.
“As we came outside, people were climbing the wall trying to get over the wall to get out of the spaces. It was just crazy.”
The navy said shots were fired in the building where about 3,000 people work. Staff were ordered to take cover where they stood. Streets in the area were closed. The building houses Naval Sea Systems Command, the largest of the Navy’s five system commands and accounts for a quarter of the Navy’s entire budget. It builds, buys and maintains the Navy’s ships and submarines and their combat systems.
The US Federal Aviation Administration halted arrivals to Washington Reagan National Airport from major airports, according to an agency website. The flights were being halted for “security,” according to the fly.faa.gov website.
Agencies