There was no report of any casualty as the truck driver and his assistant had jumped off the vehicle, the police said.
The accident occurred when the truck laden with boulders was on the rail tracks after crossing railway crossing gate number 62 which the gateman had forgotten to close, Balmikinagar station master A K Jha said.
The Muzaffarpur-Gorakhpur passenger train was pulled to Balmikinagar station by another engine to proceed on its onward journey, he said.
An action has been initiated against the gate man, Jha said.