Police briefly evacuated hundreds of workers and tourists from the US Capitol and its adjacent visitors centre amid an alert officials tentatively blamed on a faulty kitchen fan.

US Capitol.

US Capitol. Image by Nicolas Raymond / CC BY 2.0

“There are no signs of smoke or fire,” said Kimberly Schneider, a spokeswoman for the US Capitol Police. Within an hour after alarms sounded, employees returned to the building and tourists were readmitted shortly after that.

In an email to congressional workers from Capitol Police, officials said two alarms were triggered in the visitor centre, which they said was apparently caused by “a known problem with environmental controls with the kitchen exhaust fan”. It provided no additional detail.

Politicians are in recess this week.

The evacuation occurred two days after a bomb squad destroyed a pressure cooker found in an unattended “suspicious” vehicle on the National Mall near the Capitol and the vehicle’s owner was arrested.

Almost six weeks earlier, a man was arrested after he flew his gyrocopter through restricted air space and on to the Capitol grounds.

(Press Association)