The incident took place when three workers were cleaning a safety tank at the factory. When they failed to come out of the tank, the factory owner along with another worker went inside the tank to look for them, an official said.
However, the factory owner and three workers died while another worker fell critically ill after they inhaled a poisonous gas, the official added.
On hearing the news of the mishap, District Magistrate Anil Dhingra and SP Alankrita Singh rushed to the spot with a police team.