A fire damaged the LCS-1 the first Littoral Combat Ship, Freedom, under construction at Marinette Marine Corp.
Authorities suspect a welding accident triggered the fire.
According to reports, a Marinette Fire said the fire started in a berthing area where workers were using welding and grinding equipment. It took about an hour to extinguish.
Fire officials did not immediately release an estimate of the damage. No injuries were reported.
The Freedom is expected to be the Navy's first littoral combat ship for use close to shore.
Workers were finishing the 377-ft. vessel as it floated in the Menominee River
. It was about 80 percent done at the time of the fire and due to be delivered next year.
The company's senior vice president for Washington, D.C., operations, said the shipyard and the Navy would
investigate the fire. Fire officials are conducting an investigation as well.
Freedom's price tag, $350 million and counting, has sparked controversy and led the Navy to terminate a contract for a second ship that was to have been assembled in Louisiana, reports indicate.