Terminal four at London's Heathrow airport was being evacuated on Tuesday after a suspicious package was found, passengers said.
"The tannoy is telling everyone to evacuate the terminal. They're saying a suspect package has been found," one passenger told Reuters.
Officials at the airport could not confirm that the terminal was being evacuated but said a suspect bag had been found.
"In response to a suspect bag in Terminal 4, secondary searches are now being carried out on departing passengers," BAA, which manages the airport, said in a statement.
"Contingency plans have now been activated," it said. "We are working with the police to bring a swift resolution to the incident."