An oil platform has exploded off the Louisiana coast, the second such accident in the Gulf of Mexico in less than five months.

The Coast Guard said no oil had leaked and no one was killed.

The Coast Guard initially reported an oil sheen a mile long had begun to spread from the site of the blast, about 200 miles west of the source of BP's recent massive spill. But hours later, coastguard Cheri Ben-Iesau said crews were unable to find any spill.

Houston-based Mariner Energy, which owns the platform, said it did not know what caused the explosion.

Mariner officials said the platform has seven active production wells, which were all shut down shortly before the fire broke out.

Louisiana governor Bobby Jindal said the company told him the fire began in 100 barrels of light oil condensate.

The Coast Guard said Mariner Energy initially reported the oil sheen. In a public statement, the company said an initial flyover did not show any oil.

Photos from the scene showed at least five ships floating near the platform. Three of them were shooting great plumes of water onto the machinery. Light smoke could be seen drifting across the deep blue waters of the gulf.

By late afternoon, the fire on the platform was out.

The platform is in about 340 feet of water and about 100 miles south of Louisiana's Vermilion Bay. Its location is in shallow water, much less than the approximately 5,000 feet where BP's well spewed oil and gas for three months after the April rig explosion which killed 11 workers.