Kolkata Police Special Task Force arrested seven persons on Thursday and recovered 90 pieces of semi-finished improvised 9mm pistols after a raid at a factory in Jamtala.
According to the police, after the accused revealed about one arms manufacturing unit running in Donnagar, Rajarhat area, the police raided the factory as well as the house of the factory owner.
Both, the factory as well as the house, have been sealed.
Four rounds of ammunition and machines for making arms have also been seized.
Further investigation is underway.