A U.S. Capitol Police officer was shot Monday at the Capitol Visitor Center complex, and the shooter was taken into custody, Capitol officials and police said.

The event unfolded with Congress on recess and lawmakers back in their districts. The White House was briefly put on lockdown, but that was soon lifted.

The shooting occurred in the Visitors Center of the sprawling Capitol Complex. Staffers, reporters and others were told to "shelter in place" and not allowed to leave their offices. The police officer who was shot was not believed to be seriously injured.

Visitors were being turned away from the Capitol as emergency vehicles flooded the street and the plaza on the building's eastern side. Police, some carrying long guns, cordoned off the streets immediately around the building, which were thick with tourists visiting for spring holidays and the Cherry Blossom Festival.

Traffic was jammed in the vicinity, but despite the obvious emergency the scene was relatively calm. A work crew on the north side of the Supreme Court, across the street, was asked to stop work and move away from the building as a precaution.

Capitol Police did not immediately return calls.