An IndiGo flight from Mumbai to Lucknow via Delhi was grounded on Saturday after a woman told the airport check-in counter that there could be a bomb on the plane, airport sources said.

The aircraft was taken to an isolated bay for a secondary ladder point check after a Bomb Threat Assessment Committee (BTAC) found the threat as specific, the sources said.

Later, security agencies declared the plane 'safe', they said.

Repeated attempts for IndiGo's reaction on the development did not fructify.

The flight was scheduled to depart at 6.05 am. It was immediately not clear as to how many passengers were on board.

A woman passenger travelling to Delhi on Go Air flight G8 329 approached an IndiGo check-in counter at T1 and informed that there was a bomb in IndiGo's flight 6E 3612, an airport source said.

The woman also showed photographs of a few people and claimed that they were a 'threat to the nation', the source said.

CISF personnel took her to the airport police station for questioning.

A BTAC was convened in CISF Assistant Commander's office, which declared the threat a specific one, the source added.