A man from France has been detained by police after a suspected firearm was discovered at Gatwick Airport.
Massive disruption has been caused at the North Terminal following the security alert at 9.30am when Sussex Police were alerted to the "suspicious actions" of the man, 41, who was seen to discard an item in an airport bin before going through security.
Explosive Ordnance Disposal (EOD) specialist officers carried out a small controlled explosion and also recovered "what appears to be a firearm" which was removed for forensic examination.
A Sussex Police spokesman said that the "viability" of the weapon had not yet been established and the suspect was being questioned.
Passengers and staff have been allowed to return to the terminal about six hours after the alert, which forced police to evacuate the site although the South Terminal remained operational throughout.
Detective Superintendent Nick May said: "The man is being interviewed as we try to determine the circumstances of the incident, but at this time it is too early to say what his intentions, if any, were.
"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.
"We are aware that there is concern about what has happened in France, but the general threat level remains the same and people should be aware as usual of anyone acting suspiciously and report any concerns immediately."
The police spokesman said: "Passengers and staff are being allowed to return to Gatwick's North Terminal after a security alert closed the building on Saturday.
"Police were called at around 9.30am following suspicious actions by a man who discarded an item in a bin at the airport. Explosive Ordnance Disposal specialists were called to the airport to investigate the item and carried out a small controlled explosion.
"Personal items and what appears to be a firearm were recovered and have been removed for forensic examination. However, the viability of the weapon has yet to be established.
"A 41-year-old man from Vendome in France was arrested at the scene at the time of the report on suspicion of firearms offences. He was 'landside' at the airport and had not checked in or passed through any passport or security checks."
Gatwick Airport posted on Twitter: "We'd like to apologise to passengers for any inconvenience while the NT incident is investigated."
A Gatwick Airport spokesman said: "Following a full and thorough search by the police, we are now able to re-open our North Terminal to passengers. Passengers should check with their airlines for information about their journey.
"Our priority is always the safety and welfare of our passengers and extra Gatwick staff are on hand to assist those who have experienced significant disruption to their journey today.
"We are working with our airlines to return North Terminal to usual operations. South Terminal is operating as normal."