A bomb threat letter found aboard an IndiGo flight that was arriving from Lucknow triggered a security scare at Kempegowda International Airport here on Wednesday, officials said.The incident occurred on IndiGo flight 6E-231, which landed safely at Terminal 1 of the airport on Wednesday morning, they added.The cabin crew found the threat letter while the aircraft was airborne and on the final leg of the journey. The pilot was immediately alerted and he subsequently informed Air Traffic Control.Following standard security protocols, the aircraft was moved to a designated isolation area after landing, and all passengers were de-boarded.CISF personnel, airport police and bomb detection teams, assisted by sniffer dogs, carried out an intensive search of the aircraft and baggage, officials said.Security checks found no suspicious objects or explosive material, and the threat was subsequently declared a hoax, they said, adding the aircraft has been cleared to resume operations.Further investigation is under way to identify the person responsible for the threat, officials said.There was no immediate reaction from IndiGo.