The accident occurred on Chakai - Jasidih road near Madhopur village.
"The persons in the bus were traveling from Champapur village in Motihari in East Champaran district to Deoghar in Jharkhand for a 'mundan' (head shaving) ceremony. The driver lost control of the vehicle and it fell into a roadside ditch," Chandra Mandi Station House Officer Ajit Kumar said.
The local villagers rushed after hearing the noise and screams of people and pulled out the injured.