A suspicous device was found during luggage screening at the F terminal, and passengers and staff were told the leave the building.

The all-clear was given just over an hour later.

Television footage showed hundreds of passengers and staff gathering along roads leading to the terminal.

"A possible explosive device showed up in an X-ray machine at the checkpoint," airport spokesman Greg Chin told the Associated Press news agency.

Bomb disposal experts were called in to investigate but the item was found to be harmless.

The terminal serves United Airlines domestic and international flights.