ABUJA — The Nigerian Safety Investigation Bureau (NSIB) has begun an investigation into an incident in which a private jet lost one of its doors shortly after departing Nnamdi Azikiwe International Airport, Abuja, on Thursday. The aircraft, a Challenger 604 operated by Triton Aviation with registration T7-SEI, was flying to Lagos. According to an incident report cited by Daily Trust, the crew reported that a door had opened while the jet was climbing a few nautical miles from the airport, and declared a Mayday. Fire and medical teams were placed on standby as the aircraft turned back. The NSIB Director-General, Capt. Alex Badeh Jr, said the jet departed at 16:12 UTC and the incident occurred at about 3,500 feet. The aircraft landed safely at 16:34 UTC, after which the door was confirmed missing. There were nine people on board, three crew members and six passengers. A video that later circulated on social media showed farmers who said they had found the door on farmland in Abuja. The bureau confirmed that the door has been recovered and is being kept at its wreckage hangar for examination. The Nigerian Civil Aviation Authority, through its spokesman Michael Achimugu, confirmed the incident and referred further questions to the NSIB. The bureau said its investigation was under way and promised to provide updates. Triton Aviation had not commented on the incident at the time of filing.