The Delhi-Kamakhya North East express train derailed as it was reaching the Raghunathpur station on Wednesday night.
More than 12 coaches of the train were reported to come off the rail.
The accident has so far caused 6 deaths and leading 100+ people injured.
A lead-in investigation has revealed that the driver had to pull the emergency break after sensing rattling tracks.
An order of investigation about the cause of the accident has been made by the railways.
Bihar CM Nitish Kumar has announced an ex-gratia of Rs.4 lakh to the families of the deceased.
The State government will also be paying for the medical expenses of the injured passengers, he added.