The deceased has been identified as Dunarsu (26), a resident of Bihar, police said.
Eyewitnesses said, the unit was running as usual, but a sudden blast happened when the labourer was cutting some object.
The intensity of the blast was so high that the victim's body was torn apart and scattered a few metres away from the spot where he was working, they said.
Pieces of iron were found strewn at the spot where the blast took place, police said adding that investigation was on to determine the cause of the blast.