A man has been caught by police at Gatwick Airport and the North Terminal has been evacuated as a precautionary measure after finding a suspicious item.
The airport said the terminal had been fully evacuated on the landside, before passport control.
Police were called at about 09:30 GMT after “suspicious actions” by a man. A spokesman said Explosive Ordnance Disposal specialists were at the scene.
Gatwick Airport has advised passengers to contact airlines for information.
Sussex Police said the man was arrested after he “discarded an item” at the airport.
Det Supt Nick May said: “At this time, we are investigating the circumstances of the incident and it is too early to say what the item may be.
“However, given the events in Paris on Friday evening, there is heightened awareness around any such incident and it is best that we treat the matter in all seriousness.”
British Airways and Easyjet said they were working with the airport and the authorities to assess the situation and any potential impact on flights.
Passengers have been advised to leave plenty of time for their journey to the airport as roads immediately around the terminal have been closed.
A statement from Gatwick Airport said passengers due to arrive into the North Terminal would be arriving into the South Terminal.
It added that landside passengers who were already at the North Terminal were being looked after in nearby hotels.
Tim Unwin, one of those passengers evacuated from the terminal, tweeted they had been moved to the Sofitel London Gatwick Airport hotel, a short distance away.
He said the hotel area was “very cramped” and “passengers are now beginning to get frustrated” and were “tired and hungry”.
Mr Unwin, a geography professor at the University of London, tweeted at 13:40 GMT: “just been told another hour (at least) before passengers are released from holding hotels.”