The incident took place near Durga Mandir premises as a fire broke out in one Ashok Mahto's house after one of the family members tried to lit gas stove which was leaking, police officials said.
Six members of the family, including Mahto, sustained burn injuries.
The injured persons were taken to a Primary Health Centre (PHC) where the attending doctors referred all of them to the Darbhanga Medical College and Hospital (DMCH) in view of their critical condition, they said.