The plant, a unit of state-run Steel Authority of India Limited (SAIL), is India's sole producer of rails and heavy steel plates.
Democratic Steel Workers Union activists came out in droves and vented out their anger against the authorities.
One of the protesting workers, Surendra, said: "Six people have been killed in the accident and in this case the authorities had not put any signboard for any emergency related services. The team, which went inside, was not aware about gas leakage and therefore, this accident took place. This is negligence on the part of administration."
Gas leakage from blast furnace occurred due to breakdown in a water pump, affecting people working nearby in the plant premises.
Union president Kaladas Daharia, lamented poor condition of contractual workers.
"Everyday accidents take place and many people are killed. But the Bhilai Steel Plant management is silent over the matter and they are only concerned about compensation. The condition of the contractual workers is very poor," said Daharia.
The injured have been admitted to a government hospital. The cause of the explosion was not immediately known.
The plant, located in Chhattisgarh, is SAIL's largest unit that produced five million tonnes of steel in 2008/09.