Police said both the vehicles were moving at high speed and the accident occurred near Chakardaha village.
"It seems that the bus driver lost control of the vehicle due to high speed. He could not see the approaching truck from the opposite direction and the collision took place," said Narpatganj Station House Officer (SHO) Mohammad Jainufuddin.
The SHO said the injured were admitted to Forbesganj Referral Hospital and Viratnagar Hospital in neighbouring in serious condition.