An oil platform in the Gulf of Mexico and operated by Houston-based Black Elk Energy burst into flames today, leaving at least two people missing and badly injuring several others.
The fire has been extinguished, Black Elk spokeswoman Leslie Hoffman said.
She said an emergency response is under way.
The US Coast Guard said 11 people were airlifted to hospitals while nine others were evacuated to other nearby energy facilities.
Search and rescue helicopters were scouring the area, located around 20km south of Grand Isle, Louisiana.
No fatalities have been confirmed but two workers are missing.
The 11 hurt included four who suffered burns and were in critical condition at Louisiana's West Jefferson Medical Center, a hospital spokeswoman said.
When it caught fire, 22 workers were aboard the shallow-water platform, which was not actively drilling or producing oil and gas, the Coast Guard said.
An oil sheen is being monitored in waters nearby. The Coast Guard said there appeared to be little risk of a major oil spill because production was shut off before the fire, and Black Elk told authorities that any spill could be as little as 28 gallons.
The latest potentially deadly offshore incident comes a day after oil giant BP Plc reached an agreement to pay record penalties of $4.5bn for its role in the 2010 Deepwater Horizon disaster, which spewed 4.9m barrels of oil into the Gulf of Mexico and killed 11 workers.