The owner of the factory, who was also injured in the fire, has been detained, Sonarpur Police Station Officer-in-Charge Paresh Roy said.
He said that five injured persons were brought to the hospital on Sunday evening. While two of them were released after preliminary medical assistance. one among the three others died.
The incident occurred at Sonarpur's Gobindopur area.
Three fire tenders were pressed into service to douse the flames which broke out at the factory at around 12.40 pm, a fire department official said.
"This was a small factory with only a tin shed. There were some finished and unfinished firecrackers at the site," the official said.
The fire was doused at around 3.40 pm, he said.
"The owner is undergoing treatment in the hospital and we are waiting for his release to question him," the police officer said.
Other materials and commodities used to manufacture firecrackers were seized from the factory, the officer added.
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