Fire and explosion ripped through a below-decks storeroom of the aircraft carrier USS Midway yesterday, injuring 16 crewmen, six seriously, and leaving two sailors missing as the Pacific fleet flattop was conducting flight training off the coast of Japan.

Late yesterday, Navy officials said the fire was out and the temperature was dropping in the damaged compartment, but residual heat and the danger of additional explosion from flammable vapors was hampering firefighters.

Meanwhile, U.S. officials were negotiating with Japanese authorities to allow the carrier to reenter its home port of Yokosuka Thursday morning. Japanese law prohibits a burning ship from entering Tokyo harbor, a Navy official said, so the carrier was scheduled to lie offshore through the night until its captain could certify the blaze is extinguished.

The fire was the 23rd serious Navy mishap this year resulting in nine deaths and follows last month's boiler room blaze aboard the guided missile destroyer USS Conyngham off the North Carolina coast, which killed one officer and injured 12 crewmen.

Last fall, a string of serious accidents prompted Adm. Carlisle A.H. Trost, chief of naval operations, to order a two-day "safety standdown" to review fleet safety procedures.

The Navy's safety record, which has been improving in recent years, was dealt its most serious blow on April 19, 1989, when 47 sailors were killed in a gun turret blast aboard the battleship USS Iowa. There were 69 serious Navy accidents in 1988 and 63 deaths; in 1989 76 accidents resulted in 104 deaths.

Yesterday, Navy officials could not determine the cause of the Midway fire that broke out four decks below the flight deck in a "damage control parts storeroom" at 12:23 p.m. Wednesday as the ship steamed 125 miles off the Japanese coast, according to Navy spokesman Lt. David Wray.

But Navy sources said the most serious injuries were suffered by a firefighting team responding to the first reports of smoke. Reports from the ship indicated, according to Navy sources, that the storeroom exploded shortly after the team arrived to "desmoke" the compartment.

Nine wounded crewmen were flown from the carrier to hospitals in Japan, where four were reported in critical condition with extensive burns. The ship's captain, A.K. Sebrowski, characterized six of the injuries as "life threatening."

As the crew battled the blaze into the night, a number of firefighters suffered heat exhaustion, Navy officials said, and later in the day, an additional team of 10 emergency medical technicians was flown to the carrier from the naval air facility at Atsugi, Japan.

The Midway, built in 1945, is the flagship of Carrier Group 5 in the U.S. 7th Fleet. It is scheduled for retirement next year.

Type: aircraft carrier

Crew: 4,431

Commissioned: Sept. 10, 1945

Home Base: Yokosuka, Japan. The Midway is the only U.S. aircraft carrier based overseas.

Background: The three Midway-class carriers (USS Midway, Coral Sea and Franklin D. Roosevelt) were the largest U.S. warships built during World War II and the first designed to wide to pass through the Panama Canal. The Midway was modernized in the '50s and '60s so that she could operate the same aircraft as more modern U.S. carriers.

SOURCES: Jane's Fighting Ships, The U.S. War Machine