Two labourers Mushtaq Ali (50) and Vijat Saha (28) were sorting iron scrap in the shop of their employer Jitender Pandey (48) at Chateswari Kalibari on the outskirts of Tinsukia town, police said.
Suddenly there was a blast in the pile of iron scrap and the three were seriously injured, the sources said.
Vijay Saha succumbed to his wound in hospital, they said.
Police investigations found a box-like object with '82-mm mortars' written on it. Such mortars are used by army, the sources said.