Deputy Superintendent of Police Nirmala Kumari said the incident occurred when driver of the bus lost control over the vehicle and collided head on with a autorickshaw near Sanhouli village killing four on the spot.
The driver of the bus managed to escape from the spot, he said adding the police seized the bus.
The deceased have been identified as Priyanka Devi (32) her one year old son Vikky Kumar, Satyaguru Kamat (38) and Shambhu Kamat (40), the DSP said adding that the injured persons have been taken to Madhubani Sadar hospital for treatment.