There were seven workers in the Attapur area Aveone Air Cooler unit at the time of the fire, a police official said.
Six bodies were recovered and search was on for the missing man, the official added.
The deceased were from Bihar and Chhattisgarh. Four of them were identified as Saddam, Ayub, Shahrukh and Irfan.
The owner had locked the factory from outside, making it difficult for the workers to escape, the official said.
Four fire tenders were pressed into service to douse the flames.
The cause of the fire is yet to be ascetained.
The police have arrested factory owner Pramod Kumar.