PARIS — A retired French police officer traveling on Air France was detained Monday after a fake bomb hidden in a lavatory forced his Paris-bound flight to make an emergency landing in Kenya, according to prosecutors.
The hoax — the fourth against Air France in recent weeks — comes amid heightened concerns about extremist violence in many countries, and aggravated passenger jitters around the holidays.
The man in custody is a former police officer who was detained upon arrival Monday at Charles de Gaulle Airport, according to an official in the prosecutor’s office in the nearby Paris suburb of Bobigny.
The official, who is not authorized to be publicly identified speaking about an ongoing investigation, did not release the suspect’s name.
Kenyan Interior Minister Joseph Nkaissery said the suspect was among six passengers questioned Sunday in Kenya. Nkaissery said Kenya alerted French authorities about the suspected involvement of this man and a traveling companion in placing the fake bomb in the bathroom. He said sniffer dogs traced the package back to their seats and the bathroom.
The arrest is part of an investigation prompted by a legal complaint filed by Air France on Monday for reckless endangerment. The lawsuit does not name a perpetrator but leaves it to investigators to determine who might be prosecuted, and allows Air France to seek damages in an eventual trial.
France has been in a state of emergency since Islamic extremist attacks Nov. 13 in Paris killed 130 people and left hundreds wounded. The Islamic State claimed responsibility for those attacks and for downing a plane Oct. 31 carrying Russian tourists out of Egypt, killing all 224 people on board.
On Sunday, Air France Flight 463 from the Indian Ocean island of Mauritius to Paris made an emergency landing in Mombasa, Kenya, after a bomb was reported aboard. All 459 passengers and 14 crew members on the Boeing 777 were safely evacuated down airplane emergency slides.
Authorities later discovered a fake explosive, rigged with cardboard, sheets of paper, and a household timer, and declared it a hoax. Air France chief executive Frederic Gagey said the homemade apparatus was apparently placed in a lavatory cabinet during the flight.
Overwhelmed with relief, the passengers arrived safely in Paris on Monday, some crying as they embraced loved ones.
‘‘We thought we were going to die. Because of the speed of the airplane going down, we thought we would crash in the sea,’’ said passenger Marine Gorlier of the French town of Melun after landing at Charles de Gaulle Airport.
‘‘I really admired the crew, because they thought it was a real bomb and they remained very serene,’’ said Antoine Dupont of the northern city of Lille. ‘‘One of my grandchildren said: ‘The slide was super!’ ’’
The Air France-KLM Group, Europe’s biggest airline, has said that last month’s Paris attacks had cost it about $54 million of revenue in the last few weeks of November alone and that it could be May before its pipeline of forward bookings returns to normal.
Five days after the assaults, Air France flights from Los Angeles and Washington to the carrier’s Charles de Gaulle hub made unscheduled landings in Salt Lake City and Halifax, Nova Scotia, respectively after phone threats called in to a reservation center at Delta Air Lines, the European carrier’s US partner in the SkyTeam alliance.
An Air France service from San Francisco to Paris was grounded in Montreal earlier this month after another threat. Authorities are scrutinizing phone records in relation to all three incidents.