The all-clear has been given US representatives to re-enter the Capitol, where Congress meets, after it was earlier evacuated when a suspicious package was detected.
"We've cleared the package, we've cleared the area, and we're now re-entering the Capitol building," Lieutenant Dan Nichols of Capitol Hill police told reporters around 18:15 pm (23:15 Irish time).
"They've examined that area thoroughly and they have not identified anything of a hazardous nature," he said, declining to specify where the search had been made.
All staff, visitors and members of the House of Representatives and the Senate were ordered outside about half an hour, from mothers clutching their children to prominent senators like Ted Kennedy.
The order came after police discovered a suspicious package, Democratic Senate leader Mr Tom Daschle said.
Police cars and black vans pulled up and special police dressed in grey uniform ploughed out, carrying tools.
"We were on the floor voting and we were told to evacuate and evacuate fast," said Democratic senator Ms Dianne Feinstein.
Groups of senators and congressmen were forced to stand on the lawn in front of the building, as police with flack jackets entered to begin a search.
Capitol police lined the steps to the Senate side of the building and ambulances waited nearby.
AFP