The fire broke out in the compressor shop of the high-security plant, Manager (Industrial Relations) of the HAL unit, S K Rout said.
He said all the six injured persons were shifted to a hospital in Vishakapatnam with burn injuries and now all of them were stated to be stable.
It had been wrongly said earlier that one of the six had succumbed to injuries on way to Vishakapatnam, Rout said.
The injured employees, including one engaged on contract, had been initially admitted to the HAL Hospital.
The fire was extinguished in about 30 minutes before it could spread to other areas.
Efforts were on to ascertain the cause of the fire and the circumstances that led to the incident, Rout said adding senior officials are examining the matter.