WASHINGTON - A fire that broke out overnight on a US Navy nuclear-powered submarine docked at a shipyard in Maine, northeast of the United States, injured at least seven people, the Navy said on Thursday.

According to a statement from Rear Admiral Rick Breckenridge, commander of Submarine Group Two, the fire broke out shortly before 6 pm Wednesday on the USS Miami, an attack submarine docked at the Portsmouth Naval Shipyard, in Kittery, Maine.

The fire, which was was declared out at 6:45 am Thursday, was limited to the forward compartment spaces, which include living as well as command and control spaces.

The injured personnel included three Portsmouth Naval Shipyard firefighters, two crew members and two civilian firefighters providing support. They were either treated on the spot or taken to a local medical facility. All have been released.

Breckenridge said the ship's nuclear reactor has been shut down for more than two months and remained in safe and stable condition throughout the event. There were no weapons on board in the torpedo room.

The cause of the fire has not yet been identified, Breckenridge said. A full investigation is taking place.

The submarine, whose home port is Groton, Conn., arrived at the shipyard in March. It is worth about 600 million dollars, and typically carries a crew of 13 officers and 120 enlisted personnel, and is armed with Tomahawk missiles.

The Miami, a Los Angeles-class nuclear-powered submarine, arrived in Portsmouth on March 1 for maintenance and upgrades to several systems. The overhaul is expected to take 20 months.