The Capitol building was evacuated Friday afternoon after a congressional aide smelled smoke on the fourth floor of the main building and alerted officials.

Congress is in recess for the July 4th holiday.

Four fire trucks drove up to the Capitol building to accompany one that had already been at the site.  A fireman climbed up a hook and ladder to the exterior of the east side of the dome.

U.S. Capitol Police Chief Terence W. Gainer said that there was no fire.  Dust settled on a fan motor in one of the fourth story offices and gave off the scent of smoke. People were allowed back into the building 40 minutes after the first call to evacuate.

Gainer said it took 20 minutes to evacuate the Capitol, and officials are pleased with the ease in which the building was cleared.

According to the Architect of the Capitol, the United States Capitol first housed the meeting chambers of the Senate and the House of Representatives in 1793.  It was burned nearly to the ground by the British in 1814, and has been rebuilt, restored and expanded. The fourth floor is occupied by offices, machinery rooms, workshops, and other support areas.

Construction crews have been working in the dome on normal maintenance.