Hindu newspaper reporting that at least three senior officials were among those killed.
According to local witnesses, the explosion was so powerful that cars parked outside the unit were flung in the air and landed 500 meters away.
The 41-year-old plant is located 600 km from the state capital, Hyderabad, and is one of India's biggest steel producers.
At least 11 people have been killed and many others injured in an explosion which ripped through a state-owned steel plant in the southern Indian state of Andhra Pradesh, police say.
Sixteen workers have been injured in the Wednesday blast that happened at the Rashtriya Ispat Nigam Limited (RINL) plant situated in the coastal city of Visakhapatnam.
Indian police officer Janardhan Singh said many workers have suffered serious burn injuries in the blast which took place when they were checking a newly-installed oxygen unit.
"The death toll is likely to go up as all the injured have sustained between 80- and 95-percent burn injuries," Singh added.
Reports said about two dozen workers and top officials were present at the plant at the time of the accident, with the