Initial reports said two people had died, but a US Coast Guard spokesman said there had been “zero” confirmed deaths.
The fire has been extinguished, the spokesman said.
The 11 injured were airlifted to hospital in Louisiana. At least four are said to be in critical condition with severe third-degree burns, according to reports.
Bloomberg reported that an oil sheen measuring about one-half mile by 200
metres was spotted near the Black Elk platform, citing the Coast Guard.
There were 26 people aboard the platform when the explosion occurred, sometime before 10:00 local time, the Coast Guard said.
The platform is located about 20 miles south-east of Grand Isle in West Delta Block 32, where Houston-based Black Elk Energy is the operator.
A Black Elk spokeswoman confirmed that there was an incident and said the company had personnel en route to investigate the scene. She said the company would issue a release with more details later this afternoon.
Black Elk chief executive John Hoffman told the Houston Business Journal that a construction crew was finishing work on a water skimmer
when, apparently, the wrong line was cut, causing the explosion.
The platform was reportedly not actively producing oil or gas at the time. No oil has been reported spilt.
The incident comes just a day after BP was slapped with a record $4.5 billion fine and criminal charges related to the 2010 Macondo deep-water disaster in the Gulf of Mexico, which killed 11 men and led to the worst offshore oil spill in US history.
The Coast Guard has set up a command centre to investigate the incident.
Privately-held Black Elk holds stakes in more than 854 wells on 155
platforms off the coasts of Louisiana and Texas, in
water depths ranging from about 10 feet to more
than 6000 feet,