WASHINGTON (AP) _ A small fire in an electrical conduit in the Rotunda of the U.S. Capitol was quickly extinguished Thursday. No one was injured but tourists were being barred from the building as an investigation continued.

District of Columbia firefighters were summoned about 7:45 a.m. after smoke was detected on the second floor. The fire was confined to a small section of five-inch conduit and was laid to debris inside the pipe, which carries wiring to several parts of the Capitol.

Most firefighters called to the scene were released within a few minutes with a few kept on hand to vent smoke from the area.

Larger-than-usual numbers of police officers were deployed inside and around the Capitol, keeping members of the public at a distance from the building.

Though most offices inside the building were functioning as normal, the building was not opened to the public at the usual 9 a.m. hour as a precaution. Tourists will be kept out of the building until firefighters complete their investigation, Capitol Police spokeswoman Carol Absher said.

Congress is in recess until Sept. 5.