Thursday's explosion marks the second disaster in the Gulf of Mexico in almost five months.
The Coast Guard initially reported an oil sheen a mile long and 100 feet wide was spreading from the site of the fire.
The leak was thought to havee been about 200 miles west of the site of BP's massive oil spill.
At a Thursday afternoon news conference, Coast Guard officials said boats at the platform have not seen any oil sheen.
The company that owns the platform, Houston-based Mariner Energy, did not know what caused the fire. Mariner Energy's Patrick Cassidy said he considered the incident a fire, not an explosion.
"The platform is still intact and it was just a small portion of the platform that appears to be burned," he said.
Mariner officials said there were seven active production wells on the platform, and they were shut down shortly before the fire broke out.
Louisiana Gov. Bobby Jindal said the company told him the fire began in 100 barrels of light oil condensate.
The platform is in about 340 feet of water and about 100 miles south of Louisiana's Vermilion Bay. Its 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 the April rig explosion that killed 11 workers.
Responding to any oil spill in shallow water would be much easier than in deep water, where crews depend on remote-operated vehicles to access equipment on the sea floor.
A Homeland Security update obtained by The Associated Press said the platform was producing 58,800 gallons of oil and 900,000 cubic feet of gas per day. The platform can store 4,200 gallons of oil.
White House press secretary Robert Gibbs said the administration has "response assets ready for deployment should we receive reports of pollution in the water."
Crew members were being flown to a hospital in Houma. The Coast Guard said one person was injured, but the company said there were no injuries. All of them were released by early Thursday evenin
Environmental groups and some lawmakers said the incident showed the dangers of offshore drilling, and urged the Obama administration to extend a temporary ban on deepwater drilling to shallow water, where this platform was located.
The Associated Press contributed to this report.