The Cannon House Office Building was evacuated Thursday after a fire alarm went off shortly before noon.
"The United States Capitol Police and the Architect of the Capitol investigated the issue and discovered a malfunctioning electrical panel. There was no reports of smoke or fire," Capitol Police spokeswoman Eva Malecki said in a statement.
Malecki said those evacuated were allowed to re-enter about an hour later.
House Minority Leader Nancy Pelosi, D-Calif., has an office in the building located south of the U.S. Capitol.
The House is not in session, and almost none, if any, lawmakers are in town with less than two weeks to go until the midterm elections. Staff are still working in the building.
The evacuation comes after several prominent Democrats, CNN, and actor Robert De Niro were sent packages that contained devices appearing to be pipe bombs.