Suspect package found at Heathrow's Terminal 5
Heathrow Airport's Terminal 5 was partially evacuated by police following the discovery of a suspect package.
Officers said a section of the departures area was cordoned off at about 1250 GMT as a precaution.
Ninety minutes later the incident had been stood down by the Metropolitan Police and the cordoned off area reopened.
BBC Home Affairs Correspondent Danny Shaw said a suspect was in police custody while the package was examined.
No new passengers were allowed to enter the building, but planes took off and landed as normal throughout the incident.
Airport operator BAA apologised to passengers, saying: "We are sorry for the inconvenience caused to passengers while police attended this incident."
Heathrow Airport handles more international passengers than any other airport in the world.
T5, which cost £4.3bn to build and opened in March 2008, is able to handle 30 million passengers a year.