Two persons, including a woman, who were detained in connection with the "hijack" scare onboard an Indigo aircraft here, were today released by police after questioning.

"Another person is still in custody," they said, adding the three of the detained were questioned over night about the entire incident.

Three passengers - Jitendra Kumar, Samir Uppal and Harpreet -- were taken into custody for questioning after their behaviour aroused suspicions inside a Indigo aircraft yesterday, police sources said.

Police are awaiting medical reports to establish whether the three passengers were in an inebriated condition.

An Airbus A320 aircraft (Flight 6E 334) of low-cost air carrier Indigo with around 163 passengers on board a flight from Goa to Delhi made an emergency landing at the IGI airport here yesterday after the airplane pilot reported to the Air Traffic Control that a "couple" of passengers were behaving aggressively and made a hijack threat.

Emergency drill was in place immediately and the aircraft was taken to the isolation bay at the airport. The threat was made about 15 minutes before the aircraft was due to land.