While two persons died on the spot, two others succumbed to their injuries in Rampurhat hospital where the eight injured were admitted.
The condition of some of them was critical, the sources said.
The incident occurred when a group of about 15 persons were making bombs at Bagtui village under Rampurhat police station.
Superintendent of Police Hrishikesh Meena himself went to the village to inquire late in the night, the sources said.
Unofficial sources said the number of deaths was much more than the official figure.
