Six sailors were killed and five were injured Tuesday when fire broke out aboard a U.S. Navy supply ship in the South China Sea, a Navy spokeswoman said.

"It appeared to be a fuel leak," the spokeswoman said, declining to be further identified. The ship was identified as the USS White Plains, which normally carries a crew of about 403 enlisted men and 25 officers.The White Plains is a food stores ship and is part of the battle group assigned to the aircraft carrier Constellation. That group is sailing home after duty in the northern Arabian Sea supporting the naval task force

in the Persian Gulf.

According to a Navy source who asked not to be named, the White Plains and other ships of the battle group left Hong Kong on Monday after a port call. The ship was only about 100 miles off the coast when the fire broke out, the source said.

The spokeswoman said the fire broke out at 2 a.m. EDT in the main engine spaces "while conducting operations" in the South China Sea. She said the five injured, who suffered burns and smoke inhalation, were evacuated by helicopter to the USS Sacramento, a combat supply ship.

In the Philippines, U.S. Air Force Capt. Donna Eggleston said the injured then were flown to a hospital at Clark Air Base 50 miles northwest of Manila. "My latest information is that all five are in stable condition," she said in a telephone interview.

"The fire is out and the ship is under tow by the . . . Sioux," the Navy said in a written statement. The Constellation, the cruiser Fox and the frigate Ouellet all assisted in the firefighting effort, it said.

"An investigation will be conducted to determine the cause of the fire. Identifications of those killed is being withheld pending notification of next-of-kin," the statement added.

A Navy official who asked not to be identified said preliminary information suggested the fire involved "a fuel leak in the boiler manifold intake on the No. 3 boiler."

The source said it was unclear at this point whether the failure involved human error or an equipment failure but added the resulting fuel fire was so hot that sailors were limited to just five-minute stints in fighting the blaze.

Navy sources said the Sioux, a fleet ocean tugboat, had been ordered to tow the White Plains to the Subic Bay Naval Base in the Philippines for repairs.

Tuesday's fire comes three weeks after an explosion in a gun turret on the battleship USS Iowa killed 47 sailors during an exercise near Puerto Rico.