At least 27 people were taken ill after toxic methane and carbon monoxide gases leaked from a blast furnace at the Durgapur Steel Plant (DSP) in West Bengal's Burdwan district on Thursday.
The incident occurred when the employees of the DSP were working at blast furnace number 2, police said.
Twenty-four of the affected workers were immediately rushed to the Durgapur Steel Plant-run hospital. Three others, standing a few metres away from the furnace, recovered within minutes and did not need hospitalisation.
Four of the critically ill workers have been admitted in the Intensive care Unit (ICU). Ten people have already been discharged after treatment, a DSP official said.
The chief of communication DSP, BR Kanungo confirmed the gas leak.
"We are yet to ascertain the reason for the emission of gases from blast furnace number 2. Subsequently, all measures have been taken to stop the leak," Kanungo told IANS over phone.
"An expert committee has been formed to investigate the incident," he added.