DSP officials said the incident occurred at around 1.15 am when Samir Chakraborty (50) and Sk Hapijul (31) were found lying unconscious in Coke Street area of Coke Oven Battery no. 3.
Five others were also taken ill due to the gas leak in the Coke Oven Battery.
All were taken first to the plant medical unit and then to DSP Main Hospital where Chakraborty and Hapijul died, the officials said.
The DSP authorities set up a probe committee to find out how the incident had occurred, the officials said adding that all assistance would be made available to the affected families.
The security-in-charge of the plant was suspended.
Angry workers demonstrated before the plant in protest against the incident.
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