The blaze, which started while workers were using a torch to cut an oil line, also critically injured at least four workers who had burns over much of their bodies. The four were being treated late Friday at the burn center at Baton Rouge General Medical Center.
Coast Guard Chief Petty Officer Bobby Nash said late Friday that a Coast Guard cutter was continuing its search into the night, and that a broader rescue effort would resume after daybreak Saturday.
The images Friday were eerily similar to the massive oil spill that killed 11 workers and took months to bring under control. The fire came a day after BP agreed to plead guilty to a raft of charges in the 2010 spill and pay a record $4.5 billion in penalties.
There were a few important differences with the Deepwater Horizon explosion that spawned one of the nation's biggest environmental disasters: Friday's fire at an oil platform southeast of Grand Isle, La., was put out within hours, rather than burning for more than a day and causing the rig to collapse and sink.
The site of Friday's blaze is a production platform in shallow water, rather than an exploratory drilling rig looking for new oil on the seafloor almost a mile deep.
A sheen of oil about a half-mile long and 200 yards wide was reported on the Gulf surface, but officials believe it came from residual oil on the platform.
"It's not going to be an uncontrolled discharge from everything we're getting right now," Coast Guard Capt. Ed Cubanski said.
Nash said late Friday that monitoring continues to show no oil is coming from the well.
Eleven people were taken by helicopter to area hospitals or for treatment on shore by emergency medical workers.
Taslin Alfonzo, spokeswoman for West Jefferson Medical Center in suburban New Orleans, said four injured workers arrived in critical condition with second- and third-degree burns over much of their bodies.
Two were sent by ambulance to the burn center at Baton Rouge General Medical Center. Two others were sent later.
A spokeswoman for Terrebonne General Medical Center in Houma said the hospital was treating two workers who were in good condition. Several other workers were taken to Lady of the Sea General Hospital in Cut Off. None was listed in critical condition, according to a spokeswoman, who wouldn't specify how many patients the hospital was treating.
The production platform owned by Houston-based Black Elk Energy is about 25 miles southeast of Grand Isle, on the western side of the Mississippi River delta. The Coast Guard said 24 people were aboard the platform at the time of the fire.
Cubanski said the platform appeared to be structurally sound. He said only about 28 gallons of oil were in the broken line on the platform.
After the April 2010 explosion on the Deepwater Horizon, that rig burned for about 36 hours before collapsing and sinking to the Gulf floor. The depth of the well blow-out — a mile below the Gulf surface — proved to be a major challenge in bringing the disaster under control.
The Black Elk platform is in 56 feet of water — a depth much easier for engineers to manage if a spill had happened.
A federal official in Washington said a team of environmental enforcement inspectors was flying to the scene.
David Smith, a spokesman for the Interior Department's Bureau of Safety and Environmental Enforcement, said the team was dispatched from a Gulf Coast base by helicopter soon after the Coast Guard was notified of the emergency. Smith said the team would scan for any evidence of oil spilling and investigate the cause of the explosion.
"This is yet another reminder that our work on oil drilling safety is not complete," said U.S. Rep. Ed Markey of Massachusetts, the top Democrat on the House Natural Resources Committee.
Black Elk is an independent oil and gas company headquartered. The company's website says it holds interests in properties in Texas and Louisiana waters, including 854 wells on 155 platforms.
The company said on its website that "our thoughts and prayers are with those who are impacted." The company said it was still collecting information and would issue a statement later.
The spill from BP's Macondo well, about 50 miles southeast of the mouth of the Mississippi River on the east side of the river delta, dumped millions of gallons of crude oil into the Gulf. It fouled beaches, marshes and rich seafood grounds.