Security forces kick-started a massive combing operation in Bihar's Munger district on Sunday - a day after Maoists killed three Government Railway Police (GRP) jawans in an attack on Sahibganj-Danapur Intercity Express.
Top officers, including additional director general of police (Railways) PN Rai, visited the place between Bhagalpur and Jamalpur where the incident took place. An FIR was lodged with Jamalpur rail police station.
Preliminary investigations hint at attackers boarding the train from Bariarpur railway station, which is not considered a Maoist stronghold, a police officer said.
Naveen Chandra Jha, Munger superintendent of police, said security forces comprising Central Reserve Police Force, Special Task Force (STF) and Special Auxiliary Police jawans along with district personnel had launched a manhunt in the morning.
"Ambush teams have also been deployed at sensitive points," he added.
Amitabh Kumar Das, superintendent of police (Railways), said the challenge was to ensure passengers' safety in trains passing through Maoist strongholds.
Maoist attacks on trains and railway stations are nothing new in Bihar, which has reported more than eight such incidents over the past five years.
Maoists attacked the Howrah-Mokama Passenger on April 8, 2007, killing two Railway Protection Force (RPF) men.
On June 20, 2012, Maoists abducted a station master in Bihar. He was later released.
Senior police officers on Sunday laid wreaths on martyred jawans in Munger's Jamalpur. Family members of the deceased were present on the occasion.