An IndiGo flight from Mumbai to Lucknow via Delhi was grounded after a woman passenger alerted the Mumbai Airport authorities of an alleged bomb threat on Saturda, official sources said.

The passenger, identified as Uma Narayan Kannadasan, 41, who was travelling to New Delhi on a GoAir flight G8-329, approached an IndiGo check-in counter and informed officials that there was a bomb on the airline's flight 6E 3612, an airport source said.

She also provided photos of some people claiming they were behind planting the bomb and could be "a threat to the nation".

The CISF immediately escorted her to the Airport Police Station and she was subjected to sustained questioning in the matter.

Meanwhile, the airport authorities declared the bomb threat as "specific" and a detailed search of all passengers was carried out.

However, the IndiGo claimed in a statement later that the woman passenger "was found to be in a mentally unsound state".

Nevertheless, the airline said it had reported the matter to the authorities and implemented the normal security protocol and the flight departed after an hour's delay, around 7 a.m.-IANS