KITTERY, Maine (AP) — A fire that caused hundreds of millions of dollars in damage to a dry-docked submarine started when an industrial vacuum cleaner sucked up a heat source of some type that ignited debris inside the vacuum, the Navy said Friday.

The vacuum had no apparent defect and was not plugged in when the fire started aboard the USS Miami on May 23, the Portsmouth Naval Shipyard said in a statement. The Navy estimates the repair cost at $400 million.

An investigation is ongoing, and additional details and a final damage assessment will be released later, the shipyard said.

The Miami arrived at the shipyard in Kittery, Maine, in March for a 20-month overhaul.

The fire damaged the torpedo room, crew quarters, and command and control areas in the front of the submarine, but the nuclear propulsion components at the back of the sub weren’t harmed. There were no torpedoes or other weapons on board at the time.

In the aftermath of the fire, all public shipyards have been directed to empty their industrial vacuum cleaners after each shift or remove them from ships, Friday’s statement said.

The Naval Sea Systems Command is reviewing all models of vacuum cleaners now used aboard ships and will issue a directive by the end of June on which models are authorized for use.

Copyright 2012 The Associated Press.

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