A software engineer, apparently not in the right mental health, cried bomb at Birsa Munda Airport in Ranchi on Monday afternoon and delayed take-off of a hopping flight to Calcutta and Bangalore by more than three hours.

Gaurav Sinha (25), a native of Hazaribagh who is "associated with" business solutions major Tata Consultancy Services in Hyderabad and was returning home, is being detained by CISF. He is likely to be sent to Ranchi Institute of Neuro-Psychiatry and Allied Sciences (Rinpas) in Kanke for treatment, police said.

IndiGo flight 6E 344,with Sinha on board, touched down in Ranchi at 12.50pm. It was scheduled to depart for Bangalore via Calcutta at 1.20pm.

According to what eyewitnesses told police, the youth began running towards the integrated terminal building soon after getting off the plane.

"When a baffled co-passenger enquired why, he cried, ' Bhago! Plane mein bomb hai... tum bhi maroge aur hum bhi marenge (Run! There is a bomb in the plane... you will die and so will I)'," Doranda thana OC Sudhir Kumar quoted Sinha as saying.

His cries triggered panic on the tarmac. "Some passengers - there were 170-oddon board - began running helter-skelter, drawing the attention of CISF jawans. The youth was stopped for questioning. He said he had boarded the flight from Calcutta," said a source at the airport.

Ranchi resident Jayant Nath Shahdeo, who was on the IndiGo flight from Calcutta, recalled that a sniffer dog was immediately pressed into service. "Everyone was shifted to a safe distance while the dog and bomb squads conducted their inspection. Nothing was apparently found, but it delayed the return flight," Shahdeo said.

Airport authorities confirmed that flight 6E 347 finally left Ranchi at 4.30pm with 179passengers and crew members on board.

Hatia DSP Shivendra Kumar said Sinha was a resident of Buttom Bazar in Hazaribagh. "He is currently in CISF custody. Details about him are being verified."

Doranda OC Kumar said preliminary probe suggested that Sinha had a history of mental illnesses. "We will refer him to Rinpas in Kanke for treatment."

A source said the youth's father, Mrinal Kumar Das, was a retired branch manager of Bank of India in Chatra, neighbouring Hazaribagh. "The father had apparently alerted the authorities at Calcutta airport about his son's health status, seeking help in boarding the plane."

These details could not be independently confirmed by this correspondent.