The victims were packing chemicals when the blast, caused by friction, ripped through the godown of the factory at Annanagar near Alangudi here last evening, they said.
K Muthu (42) was killed on the spot, while two persons, injured in the mishap, had been admitted to government hospitals here and neighbouring Thanjavur.
Police said the workers had not made proper arrangement before starting their work. They had strewn the explosive chemicals all around and were surrounded by the finished and unfinished fireworks items.
The entire shed was blown up in the explosion, they said.