The blast on the train was "not very loud", said an eyewitness who added that he realised something was wrong on seeing people running away.
A person at the station told IANS: "The blast sound was not very loud. On seeing people running away from the train we knew something was wrong."
He said there was not much of a damage to the rail coach and only a seat was damaged. Inside the compartment, the passenger baggages were strewn around.
Later, the police cordoned off the area, he said.
One woman was killed and 11 injured when two bombs in two coaches of the Bangalore-Guwahati train blew up Thursday at the Chennai railway station.