The passengers received minor injuries when they jumped out of the train in panic, the police said.
The driver of the Lucknow-Barauni express applied the emergency brake when the train ran over a buffalo among a herd that was crossing the tracks at Sadajagat halt under Samastipur division and two bogies jumped the track, the police said.
The train left for Dalsingsarai railway station after detachment of the two bogies.