- NEW: Fire was not out six hours after initial response
- Fire on nuclear submarine injures six
- No weapons are on board the vessel
- Reactor not affected, officials say
(CNN) -- Firefighters were still battling a blaze in a nuclear submarine late Wednesday at a U.S. Navy shipyard in Maine - six hours after their initial response to it, a shipyard spokesman said.
Six people sustained injuries and subsequently received treatment either on the scene or at "a local medical facility", said Captain Bryant Fuller, Shipyard Commander for Portsmouth Naval Shipyard in Kittery. Among them was a firefighter evacuated due to heat exhaustion. Fuller described the man as "conscious and alert," in a statement read aloud to journalists.
"While the fire is not out, the situation is improving," he said at 11:45 p.m. Eastern time. "Due to the heat created by the fire, steam continues to emit from the ship from the firefighting efforts."
The USS Miami's reactor was not operating at any time the fire broke out and has remained unaffected and stable throughout, he said. The sub was in dock at the shipyard, when the blaze began, where it has been "since early March for an overhaul."
The fire started in a forward part of the ship away from the reactor, affecting "primarily living areas and command and control spaces," Fuller said.
The USS Miami is capable of carrying Tomahawk cruise missiles and Mark 48 torpedoes, but no weapons were on board, said Navy spokesman Lt. Myers Vasquez.
Local firefighters assisted the Navy's fire crew, who initially responded to the blaze at 5:41 p.m., Fuller said. State, local, and federal authorities were notified of the incident.
"The cause of the fire is not known at this time," Fuller said. " A full investigation will be conducted."
The Miami is a fast-attack submarine of the Los Angeles class, Vasquez said.
Portsmouth Naval Shipyard was established on June 12, 1800 and is the oldest continuously operating shipyard operated by the Navy, according to Gary Hildreth, a public affairs officer for the facility.
CNN's Larry Shaughnessy and CNN's Chris Boyette contributed to this report.
