Five new explosions jolted a burning Norwegian supertanker yesterday in the Gulf of Mexico, accelerating its spill of light crude oil into the water 57 miles from the Texas coastline southeast of Galveston.

Salvage teams prepared to begin putting out the fire on the Mega Borg at sunrise this morning, Coast Guard officials said. Until the fire is extinguished, they said, the spill cannot be contained and the cause remains unknown.

The stern of the 853-foot-long tanker, where the fire is concentrated, began to tilt yesterday, raising fears the ship may be taking on water or that its cargo has shifted.

The Mega Borg is carrying about 38 million gallons of light crude oil, but officials could not be precise about how much oil has spilled so far. An oil sheen about 17 miles long and 200 yards wide was trailing the vessel. The Exxon Valdez spilled 10.9 million gallons of heavy crude oil last year in Alaska.

In addition to posing a threat to Texas's recreational shore, the oil is spilling in an area of commercial fishing, primarily shrimp, according to the Coast Guard.

Yesterday's explosions, which began about 12:15 p.m. CDT and ended 10 minutes later, followed explosions Saturday that started after the Mega Borg had begun the delicate procedure of "lightering," or transferring its cargo to a smaller tanker.

The initial explosion and fire at 1 a.m. Saturday killed two of the 41 crew members and injured 17 others, most of whom were treated after being evacuated. Two crew members are still missing and presumed dead after a search for them was called off.

In Lake Jackson, Tex., crewmen from the vessel told the Associated Press that they had to feel their way along smoke-filled corridors to the deck to escape Saturday.

The explosions yesterday came after three people from the Smit America Galveston Bay Salvage Team -- hired by the ship's owners -- had been aboard for about four hours shutting off some of the valves to the vessel's tanks. They left before the new round of explosions began.

The explosions were described by Coast Guard officials as very loud and powerful, causing burning crude oil to roll off the stern into the water. The stern has dropped by 58 feet since Saturday, officials said.

"We're not sure what that means," Chief Petty Officer Richard S. Muller said yesterday from Galveston. The stern appeared to have stabilized about five feet above the water late last night, officials said.

Three Smit America ships sprayed water on the Mega Borg's deck to try to cool the tanker, officials said. Two Coast Guard cutters also flanked the tanker. A high-seas barrier boom has been brought in to corral the spilled oil once the fire is out.

A commercial C-130 airplane dropped dispersant over parts of the spill within a five-mile radius of the tanker late last night, the Coast Guard said. Dispersants are used to make oil break up more quickly.

Foam will be spread over the ship's stern this morning, officials said. "They didn't want to start putting it out until they felt they had enough light," Muller said.

The Mega Borg was headed for Aruba from Angola.