The gas leakage occurred in furnace wing of the plant. Eight of the workers collapsed after inhaling the gas while others managed to escape in time.
Eye witnesses said two workers died on the spot. Six others were shifted to nearby hospital, where four workers succumbed.
The deceased have been identified as B. Ranganath, 21, K. Manoj, 24, S.A. Wasim, 39, U. Gangadhar, 37, Guravaiah, 40, and K Siva Maddileti alias Lingaiah, 26.
Gerdau Steel, one of the largest steel companies worldwide, said it had suspended operations at the unit and will resume only after an extensive safety inspection.
"Gerdau sadly informs that an accident occurred at its Tadipatri steel plant, in India, this evening, resulting in six causalties. Gerdau immediately provided medical assistance and the workers were sent to the local hospital," the company said in a brief statement.
"The company is assisting the family of the victims and is working to determine the cause of the accident. The company is also extending all cooperation to local authorities," it added.
Gerdau is the leading producer of long steel in the Americas and one of the largest suppliers of special long steel in the world. It has more than 45,000 employees and industrial operations in 14 countries, according to the information on its website.
The plant in Andhra was Gerdau's first in Asia and it has capacity to produce 300,000 tons of special steel per year.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)