Media reports have revealed that the crash of an EgyptAir plane in 2016, which killed all 66 passengers, was caused by a cigarette smoked by the pilot.

Investigators into the crash of EgyptAir Flight MS804 from Paris to Cairo claimed that in a 134-page official report sent to the Paris Court of Appeal last month, the first captain had been smoking at 37,000 feet shortly before the crash, according to The Independent. The newspaper added that investigators indicated that the fire may have broken out in the cockpit due to a mixture of a burning cigarette and oxygen leakage from the co-pilot’s mask.

Italian newspaper Corriere Della Sera has also published a new report, claiming that a microphone recorded a hissing sound on the mask. “Oxygen checks in the cockpit are a routine part of the pre-flight activity,” Daniele Veronelli, a member of the Italian National Association of Commercial Aviation Pilots, told the newspaper. According to the report, the report explained that the oxygen mask was changed three days before the trip and set to emergency mode designed for smoke or fumes in the cockpit.

In May 2016, EgyptAir announced that Flight MS804 had disappeared from radar after entering Egyptian airspace. At the time, the Egyptian authorities blamed a terrorist bombing for the incident. However, the official French organization responsible for technical investigations of civil aviation accidents and incidents, BEA, said, in 2018, that the most likely hypothesis was that a fire broke out in the cockpit while the plane was in flight and that the fire spread rapidly, resulting in the plane losing control.