KITTERY — Navy officials said this morning that it is too early to tell whether the nuclear submarine USS Miami, which burned for more than eight hours before being extinguished this morning, will ever sail again.

The Navy planned to send investigators into the forward section of the submarine, where the fire was located, to determine the cause, said Rear Admiral Rick Breckenridge, commander of Submarine Group Two based in Groton, Ct. in remarks to reporters at the main gate of the Portsmouth Naval Shipyard.

Breckenridge said that officals have moved from fighting the fire to a recovery mode.

He said it was premature to say whether the Miami, which cost $900 million, was salvageable or is too badly damaged to be repaired and put back in use. The Miami is in the third month of a planned 20-month overhaul.

Seven firefighters received minor injuries while fighting the fire.

Breckenridge praised the repsonse of firefighters from communities in Maine, New Hampshire and Massachusetts that responded to the blaze.

“As I stand before you today, there are a lot of heroes who worked together to save the ship,” Breckenridge said. He said local firefighters worked inside the submarine in conditions of high heat, smoke and cramped quarters.

Many of them, he said, had never been on board a submarine before.

A spokesman for Rep. Chellie Pingree, D-Maine, said the congresswoman planned to visit the yard at noon to thank the first responders and view the damage to the sub. Pingree is a member of the House Armed Services Committee.

Breckenridge said the high heat and difficulty extinguishing the fire, was largely because the fire spread to insulation. The fire also was fueled by cabinets and lockers in the living quarters and command area.

Robert McAleer, of the Maine Emergency Management Agency, said that five Maine communities sent crews to the shipard to help fight the fire on the Miami.

“Their actions were almost beyond comprehension,” McAleer said. The fact that the damage was not more extensive was “pretty remarkable,” he said.

Breckenridge said the fire was confined to the forward part of the ship and what he described as the upper and middle levels.

That area contains the crew living quarters, command and control, and the torpedo room. There were no torpedos on board the Miiami, he said.

The forward part fo the ship was evacuated when the fire broke out.

Crews continued to man the nuclear reactor.