A mile-long oil sheen spread Thursday from an offshore petroleum platform burning in the Gulf of Mexico off Lousiana, west of the site of BP's massive spill.

Coast Guard Petty Officer Bill Coklough said the sheen, about 100 feet wide, was spotted near the platform owned by Houston-based Mariner Energy Inc.

He said Mariner had deployed three firefighting vessels to the site and one already was in place fighting the blaze.

The Coast Guard says no one was killed in the explosion and fire, which was reported by a commercial helicopter flying over the site around 9 a.m. CDT. All 13 people aboard the rig were rescued as they floated in the nearby water in survival outfits called gumby suits.

The platform is in about 340 feet of water and about 100 miles south of Vermilion Bay on the central Louisiana coast. It's location is considered shallow water, much less than the approximately 5,000 feet where BP's well spewed oil and gas for three months after an April rig explosion.

All 13 people aboard the rig were found floating in the water, sticking close together, Coast Guard spokesman Chief Petty Officer John Edwards said.

"These guys had the presence of mind, used their training to get into those gumby suits before they entered the water. It speaks volumes to safety training and the importance of it because beyond getting off the rig there's all the hazards of the water such as hypothermia and things of that nature," Edwards said.

All were being flown to a hospital in Houma to be checked over. Coast Guard Cmdr. Cheri Ben-Iesau said one person was injured, but the platform's owner, Houston-based Mariner Energy, Inc., said there were no injuries.

"Mariner has notified and is working with regulatory authorities in response to this incident. The cause is not known, and an investigation will be undertaken," the company said in a statement. It said the platform was located on Vermilion Block 380, approximately 100 miles off the Louisiana coast.

The platform is a fixed petroleum platform that was in production at the time of the fire, according to a homeland security operational update obtained by The Associated Press.

The update said the platform was producing about 58,800 gallons of oil and 900,000 cubic feet of gas per day. The platform can store 4,200 gallons of oil.

Seven Coast Guard helicopters, two airplanes and three cutters were dispatched to the scene from New Orleans, Houston and Mobile, Ala., Ben-Iesau said. She said authorities do not know whether oil was leaking from the site.

White House press secretary Robert Gibbs said President Barack Obama was in a national security meeting and did not know whether Obama had been informed of the explosion.

"We obviously have response assets ready for deployment should we receive reports of pollution in the water," Gibbs said.

Mariner Energy focuses on oil and gas exploration and production in the Gulf of Mexico. In April, Apache Corp., another independent petroleum company, announced plans to buy Mariner in a cash-and-stock deal valued at $3.9 billion, including the assumption of about $1.2 billion of Mariner's debt. That deal is pending.

Apache spokesman Bob Dye said the platform is in shallow water. Responding to any oil spill in shallow water would be much easier than in deep water, where crews depend on remote-operated vehicles access equipment on the sea floor. Mariner said in initial flyover for no hydrocarbon spill.

A company report said the well was drilled in the third quarter of 2008.

The platform is about 200 miles west of BP's blown-out well. On Friday, BP was expected to begin the process of removing the cap and failed blowout preventer, another step toward completion of a relief well that would put a finals eal on the well. The BP-leased rig Deepwater Horizon exploded April 20, killing 11 people and setting off a three-month leak that totaled 206 million gallons of oil .

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Associated Press writers Janet McConnaughey in New Orleans, Chris Kahn in New York and Eileen Sullivan, Matthew Daly and Gerry Bodlander in Washington contributed to this report.