"The explosion occurred at an isolated place on platform number 10. It was a crude bomb and one person has been injured," SSP Manu Maharaj told reporters here.
The incident came just hours before BJP Prime Ministerial candidate Narendra Modi was to address a rally in the Bihar capital, for which BJP had made extensive arrangements to bring the people to the city.
RPF sources said that the explosion took place in a paid toilet at the station.
The SSP said that bomb disposal and forensic teams have reached the spot and the area was being sanitised.