HONOLULU (AP) _ An oil tanker that ran aground floated free when salvage workers lightened the ship's load to prevent more crude oil or fuel from spilling into the Pacific Ocean and washing up on Hawaii's beaches.

The 800-foot Exxon Houston ''suddenly just started floating,'' Coast Guard spokesman David Goff said Friday night.

Officials had planned to wait until high tide early today but workers who pumped off more than 9,400 tons of ballast water and some of the remaining 3.8 million gallons of crude oil lightened the ship enough so that it floated free on its own, said Scott Hartvigsen, another Coast Guard spokesman.

He said the ship was being towed to deeper water and two ships would stay with it overnight ''but everything's going great so far.''

Officials today were to assess the damage to the ship, as well as the extent of the oil spill, already in the thousands of gallons, he said.

Meanwhile, state and federal agencies launched a cleanup of the thick, smelly oil washing in along a 2-mile stretch of little-used shoreline 15 miles west of Honolulu and famed Waikiki Beach.

High winds and rough seas tore the vessel from its offshore mooring Thursday night. It ran aground on a coral reef and ruptured a fuel tank.

A local oil spill cleanup cooperative, called the Clean Islands Council, was on the scene, said Les Rogers, spokesman for Exxon Co. USA, the Houston- based domestic oil and gas division of Exxon Corp. The Coast Guard's Pacific Area Strike Team was en route to help in the cleanup.

Exxon Co. USA, will pay for the costs of the cleanup, according to Exxon attorney Leonard Alcantara.

The Exxon Houston had unloaded 400,000 barrels of Alaska crude oil at an offshore mooring a mile off the Hawaiian Independent Refinery when it tore free, said Capt. Gordon Piche, commanding officer of the Coast Guard's Marine Safey Office.

The skipper, Captain Kevin Dick, notified the Coast Guard there was no need for assistance, but 2 1/2 hours later, the ship radioed it had run aground in 27 feet of water about one-third mile offshore of Barbers Point, located on the southwest corner of Oahu, Hawaii's main island, Piche said.

When the ship tore away from its mooring, floating hoses unloading the oil pulled free, spilling about 25,000 gallons of crude oil into the sea.

Although valves automatically closed, the oil spilling from the hoses created a three-mile-long oil slick spreading parallel to the shore to the east toward Honolulu. By Friday night, it was dissipating and posed no immediate threat to the shoreline, officials said.

When the ship ran aground, one of the vessel's fuel tanks ruptured, spilling about 92,000 gallons of the thick black oil, much of it washing ashore, fouling the sand and coral rocks.

Libert K. Landgraf, deputy director of the Department of Land and Natural Resources, said there was no immediate evidence of injury or death to marine life or birds.

Oil washed up on a beach where a popular tourist luau is held, prompting the state Department of Health to post ''Polluted Waters'' signs, and at other areas as far as two miles to the north, said Coast Guard spokesman Dennis Hubbard.

Meanwhile in the Florida Keys, an oil slick about 2 miles long and a quarter-mile wide was reported Friday about 10 to 12 miles off the north Key Largo coast, said to Coast Guard spokesman Joe Dye.

The origin of the oil had not been determined, but Coast Guard marine safety office spokeswoman Lynn Mountcastle said it could have been bunker oil released by a ship.