The White House was locked down Saturday morning as the President and First Lady were about to leave for Selma, Alabama.
Reporters and photographers waiting outside the residence to watch the departure from the South Lawn were abruptly ordered back inside by Secret Service agents, who them locked them inside the press briefing room.
Agents were seen patrolling the grounds, and standing by vehicles at the North Portico, on the other side of the executive mansion.
At the same time, a tour group was evacuated from the White House.
Reporter David McCumber of Hearst Newspapers reported hearing a loud noise at the time, and photos on Twitter showed what appeared to be a fire on nearby 17th Street.
President and Mrs. Obama were leaving to fly to Selma for the 50th anniversary of the civil rights march there.