There were seven workers in the Attapur area factory during the time of the fire.
Four charred bodies were recovered and search was on for the missing men, a police official said.
The deceased, all from Bihar, were identified as Saddam, Ayub, Shahrukh and Irfan.
The cause of the fire is suspected to be a short-circuit.
The owner had locked the factory from outside, making it difficult for the workers to escape, the official said.
The police have arrested factory owner Pramod Kumar.