"These submarines were designed decades ago. So they're no longer state of the art," analyst Loren Thompson said. "If this vessel returns to service, I will be amazed."

Working in the submarine's favor is the fact that workers had removed some equipment and gutted part of the vessel during a retrofit, said U.S. Rep. Chellie Pingree after meeting with the shipyard commander.

Breckenridge said it was premature to say whether the submarine could be salvaged.

Ships in the USS Miami's class cost about $900 million at the time to build. The newest attack submarines, the Virginia class, cost about $2.6 billion apiece.

The fire broke out Wednesday evening while the Miami was on a 20-month stay at the shipyard for an overhaul, and it took firefighters from more than a dozen agencies until Thursday morning to put out the fire, described as intense and smoky.

Pingree described it as a "hot scary mess."