Four persons were killed and one was seriously injured in an explosion in a fire cracker factory at Naihati in West Bengal's North 24 Parganas district, police said.
The explosion took place at around 3:30 pm inside the fire cracker factory and its four workers died on the spot, a senior police officer said.
Another worker of the factory was seriously injured in the blast, he said.
Ten fire engines have been rushed to the spot to douse the flames, he said.