The incident took place as a SUV carrying three policemen collided head-on with a truck in which the SI Sanjeev Kuamr Rajak died on the spot.
Manish Kumar (ASI) and Phool Chand (constable) were injured , Ballia police station in-charge Ratesh Kumar Ratan said.
The injured were admitted to a government hospital.
The police personnel were travelling by the SUV to Patna from Purnia on official work.
The truck driver escaped from the spot after the accident, Ratan said.