The mishap took place as the driver tried to avoid running over cattle and in the process lost control of the bus, the sources said.
Five persons, identified as Chhotu Singh (18), Bhanwar (20), Sukesh Chaudhary (20), Umesh Singh (15) and an unidentified persons died, while 26 others suffered injuries, they said.
The bodies have been sent for post-mortem and the injured admitted to a hospital where the attending doctors referred six seriously injured persons to the PMCH, Patna.
The bus was going from Ara to Maliabagh in Bhojpur district.