The incident occurred at Sonarpur's Gobindopur area and the owner of the factory has been detained.
Three fire tenders were pressed into service to douse the flames which broke out at the factory at around 12.40 pm on Sunday, they said.
"This was a small factory with only a tin shed and small walls on four sides. There were some finished and unfinished firecrackers at the factory. So far, six persons were injured in the mishap. They have been sent to a nearby hospital," a fire department official said.
"We have detained the owner of the factory for questioning and trying to find out what was the cause of the fire," the officer said adding that the fire was brought under control.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)