WASHINGTON — Police briefly evacuated hundreds of workers and tourists from the U.S. Capitol and its adjacent visitors’ center on Tuesday in a problem officials tentatively blamed on a faulty exhaust fan in a visitor center kitchen.

“There are no signs of smoke or fire,” said Kimberly Schneider, a spokeswoman for the U.S. Capitol Police. Within an hour after alarms had 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 center, which they said was apparently caused by “a known problem with environmental controls with the kitchen exhaust fan.” It provided no additional detail.

Lawmakers are in recess this week for the weeklong Memorial Day break.

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 Florida man was arrested after he flew his gyrocopter through restricted air space and onto the Capitol grounds.

In Tuesday’s incident, police cleared the East Lawn and closed First Street between the Capitol and the Library of Congress until the buildings were reopened.

Fink Arthur, a 28-year-old tourist from Freiborg, Germany, said he was with a tour guide and initially was told it was probably just a test, but then the guide led people out of the building.

Denise Grandits of Buffalo, New York, said she and 70 eighth-graders were touring the Capitol and heard the alarms. She said the guide escorted them out of the building.

“We just walked. It was pretty calm,” she said.

According to the police email, officials initially thought one of the two alarms that were triggered was in the Capitol and they began evacuating that building.

In a moment of confusion, police advised people in the Capitol a short time later that they could remain inside because the alarms were not coming from that building. They reversed themselves again minutes later and resumed evacuating the Capitol.

The email said once officials determined both alarms were in the visitor center, they decided to continue emptying the Capitol “to ensure staff and members did not receive conflicting information.”