Police said that the mishap occured between Kasta and Paraiya stations under Gaya-Mughalsarai section of the East Central Railway.
No casualty or injury has been reported so far.
District SP Sushil Khopde said that a medical team has been sent with the rescue train to the spot. He said that the explosion took place shortly after the train had left Gaya station.
Railway sources said that the passengers have been taken to Mughalsarai by the rescue train from where they will be sent to New Delhi by a special train arranged for the purpose.
Maoists, who have called for 48-hour bandh in seven states, inclduing Bihar, are suspected to be behind the incident.
On Mar 22, CPI (M) called 48-hour bandh in Bihar, Jharkhand, Orissa, West Bengal, Chhattisgarh, Andhra Pradesh and three districts of Maharashtra in protest against Operation Green Hunt.
Meanwhile, Moaists have reportedly blasted railway track near Rourkela, Orissa. One goods train have been derailed.
No injury has been reported so far. The train services between Bombay and Howrah route have been disrupted.