NAIROBI, Kenya (AP) — A fake explosive rigged with cardboard, sheets of paper and a household timer forced an Air France flight into an emergency landing in Kenya yesterday, sending hundreds of passengers down emergency slides in what the airline’s CEO Frederic Gagey said was the fourth bomb hoax against the airline in recent weeks.

The home-made apparatus was discovered around midnight, hidden in a lavatory cabinet behind a mirror where it was apparently placed during the approximately 11-hour flight to Paris from the island of Mauritius, said Gagey. He said the airline has had heightened security checks around the world since the November 13 attacks that left 130 people dead in Paris.

“It was an ensemble of cardboard, papers and something that resembled a kitchen timer. Nothing that presented a danger to the plane, to the passengers or to the crew,” a visibly irritated Gagey told a news conference in Paris. He said it contained no explosives.

With France in a state of emergency since the Paris attacks and the United States on high alert since the attack in San Bernardino, California, that left 14 dead, hoaxes present a particular conundrum for security officials, who must choose between feeding mass fear and keeping the public in potential danger.

Last Tuesday, the two biggest school systems in the US — New York City and Los Angeles — received threats of a large-scale jihadi attack. LA reacted by shutting down the entire district, while New York dismissed the warning as an amateurish hoax and held classes.

Air France has been the target of three prior hoaxes, all in the United States, Gagey said. The fourth came on board the flight from Mauritius, a popular winter vacation spot for French tourists.

The Boeing 777 was heading to Charles de Gaulle airport in Paris when its pilots requested an emergency landing early yesterday at Kenya’s coastal city of Mombasa.

Gagey congratulated the crew for their cool-headed reaction to divert the plane to Moi International Airport. A safety check was carried out in the bathroom before the flight, he said, indicating the device was placed in the cabinet while the plane was in the air. He denied any security failure in the flight, saying that passengers are checked and sometimes double-checked on flights.

Six passengers were being questioned, including the person who informed the crew about the device, said a Kenyan police official who is part of the investigation and who insisted on anonymity because he is not authorised to speak to the press.

Passengers praised the cool-headed response of the flight crew.

“The plane just went down slowly, slowly, slowly, so we just realised probably something was wrong,” said Benoit Lucchini, who was headed home to Paris on the flight.

“The personnel of Air France was just great, they were just wonderful. So they keep everybody calm. We did not know what was happening,” said Lucchini. “So we secured the seat belt to land in Mombasa because we thought it was a technical problem, but actually it was not a technical problem. It was something in the toilet.”

The plane, carrying 459 passengers and 14 crew members had left Mauritius at 9:00 pm, said Kenyan police spokesman Charles Owino. All passengers were safely evacuated and the device was removed, he said. The passengers were flown to Paris on a special flight late yesterday.