There were other labourers too at the site at the time of the incident. Some of the others were buried for a while under rubble following the blast.
The incident took place near Arjundaha village of Pakur district, around 500 km from state capital Ranchi.
Police are searching for the owner of the mine, and say the mining was taking place illegally.
Police sources said more than 150 stone mines are operating illegally in Pakur. Stone extracted from here is supplied to stone crushers for making chips used in building construction.