The US Capitol Building and the US Capitol Visitor Center were evacuated after alarm sounded in both buildings, police said.
The cause of the alarm was under investigation by the US Capitol Police and the DC Fire Department, US Capitol Police spokeswoman, Kimberly Schneider, said on Tuesday . However, she said that signs of smoke or a fire have not been found.
All staff and other personnel were directed to remain in their assembly area until further notice. The House and Senate are on recess and the law-makers were not in session when the evacuation happened.
Police have also closed nearby streets in connection of the incident.