A bomb disposal police unit has been sent to Gatwick airport after a “suspected prohibited item” was found in luggage.
Sussex Police said a “security cordon has been put in place” inside the south terminal of the UK’s second busiest airport.
A large part of the building has been evacuated.
Travellers flying from the south terminal have been unable to check-in since the incident began.
Sussex Police said in a statement: “Police were called to the south terminal at Gatwick airport at 8.20am on Friday following the discovery of a suspected prohibited item in luggage.
“To ensure the safety of the public, staff and other airport users, a security cordon has been put in place whilst the matter is dealt with.
“As a precaution, an EOD (explosive ordnance disposal) team is being deployed to the airport.
“This is causing significant disruption and some roads around the south terminal have been closed.
“We’d advise the public to avoid the area where possible.”
A spokesman for Gatwick said: “A large part of the south terminal has been evacuated as a precaution while we continue to investigate a security incident.
“Passengers will not be able to enter the south terminal while this is ongoing.
“Safety and security of our passengers and staff remains our top priority.
“We are working to resolve the issue as quickly as possible.”
The north terminal is unaffected.
Train services at Gatwick have been suspended.
Train passenger information website National Rail Enquiries said: “The police are dealing with an incident at Gatwick airport. The station and airport are currently being evacuated.
“Services are able to run through the station and area but will not call at Gatwick airport at this time.
“Please avoid travelling to the station whilst this incident is ongoing.
“This is expected to continue until approximately 2pm.”
Aviation analytics website Cirium said 316 flights were scheduled to depart from the airport on Friday, with a total of more than 60,600 seats.
A further 318 flights were scheduled to arrive, with more than 61,400 seats.
Sourse: breakingnews.ie