11:46 a.m. ET -- A man and two women were admitted to MedStar Washington Hospital Center with "severe injuries" from multiple gunshot wounds, said chief medical officer Janis Orlowski, adding that the injuries do not appear to be life-threatening.
11:42 a.m. ET -- As authorities work to clear Building 197, where the shootings happened, to ensure there are no additional shooters, Naval District Washington spokesman Ed Zeigler says that the two injured police officers are not among the fatalities reported earlier.
11:37 a.m. ET -- The top Navy officer, Adm. Jonathan Greenart, tells CNN he was evacuated from his residence at the Navy Yard when the shooting began.
11:36 a.m. ET -- "Multiple" people have been killed in the shooting, Naval District Washington spokesman Ed Zeigler says.
11:34 a.m. ET -- Two suspected shooters "are down" at the Washington Navy Yard, Zeigler says.
11:31 a.m. ET -- Helicopters are hovering over the scene, and it appears one chopper contains a police sniper.
11:18 a.m. ET -- The Bureau of Alcohol, Tobacco, Firearms and Explosives is dispatching a special response team similar to the one used to take the Boston Marathon bomber into custody, said law enforcement official Even Perez.
About 20 specially trained agents, accompanied by an armored vehicle, will work with local authorities when they arrive on the scene. ATF agents are already on the perimeter, engaged in the investigation, the ATF says.
11:12 a.m. ET -- Pentagon spokesman George Little says he believes "there has been loss of life," but he would not say how many people are believed dead.
11:07 a.m. ET -- Via Twitter, local police have issued a statement for those concerned about their loved ones: "Navy Yard: family members may reunite at Nationals Stadium Parking Lot B, South Capitol & K St SE."
11:05 a.m. ET -- Heavily armed SWAT officers were seen escorting people from the building where shots were fired.
10:58 a.m. ET -- Two witnesses tell CNN affiliate WJLA they heard their building's fire alarm go off and saw a man with a rifle as they left the building.
"He aimed the gun and fired our way," Todd Brundidge told the station. "I couldn't believe it."
People frantically tried to escape the building, he said. "They were pushing. They were shoving. People were falling down."
10:51 a.m. ET -- At least six Washington-area schools are on lockdown after the shooting, the public school system tweeted.
10:50 a.m. ET -- In addition to the injured Washington, D.C., officer, a base security guard was also injured, said Metropolitan Police Department spokeswoman Saray Leon.
10:48 a.m. ET -- About 3,000 people work at the Naval Sea Systems Command's headquarters, the Navy says.
10:46 a.m. ET -- At least 10 people have been injured in the shooting, according to police, and the U.S. Navy has issued a statement saying there are "several injuries with reports of fatalities."
10:43 a.m. ET -- The suspect in the shooting is a 6-foot tall, bald male of medium complexion, wearing a black shirt and jeans, said D.C. Metropolitan Police spokesman Chris Kelly.
10:40 a.m. ET -- Counterterrorism officials have briefed President Barack Obama "several times" about the shooting, a White House official says.