An Ahmedabad-bound IndiGo flight from here was delayed by over eight hours on Wednesday after a tissue paper with ‘Danger’ written on it was found in the aircraft immediately after the pushback, officials said.The aircraft was then taken to an isolation bay, where a thorough search of the passengers, their baggage and the aircraft was carried out but nothing suspicious was found, they said.A case was registered against an unidentified person, police said.”At 1.32 am, an IndiGo pilot reported to the Air Traffic Control (ATC) that a tissue paper bearing the word ‘Danger’ was found in the flight (6E 911). The aircraft had pushed back at 1.21 am. The tissue paper was located in the front galley (kitchen area) of the aircraft, underneath a crew folder,” sources told PTI.The flight was scheduled to take off from the Chhatrapati Shivaji Maharaj International Airport at 1.30 am and land in Ahmedabad at 2.50 am. However, it took off at 9.48 am and reached the destination at 10.36 am, as per live flight tracking website flightradar24.com.An official of Sahar police station said, “The staff found a tissue paper with ‘Danger’ written on it inside a toilet. The airport authorities immediately alerted the Mumbai police’s control room and also contacted the nearest police station. A Bomb Detection and Disposal Squad was rushed to the spot, and a thorough search of the aircraft was carried out. However, no suspicious object was found.”Police later registered a case against an unidentified person and launched an investigation, the official added.IndiGo refused to issue a statement.