The Portsmouth Naval Shipyard Fire Department responded Wednesday to a report of another potential fire aboard the USS Miami submarine, but it turned out to be a false alarm. The shipyard said that an alarm activated at just before 9 a.m. aboard the sub, but there was no fire. The nuclear-powered submarine was severely damaged by a fire May 23 while the ship was in dry dock for an overhaul at the shipyard in Kittery. The Navy is investigating the cause of that fire, the extent of the damage, and whether the Los Angeles-class submarine can be repaired.