The cause of the offshore oil platform fire off the Louisiana coast that sent four workers to the hospital is under investigation.

The blaze was reported around 2:30 Thursday morning.

Video, posted online by the environmental action group "Alabama Coast United" shows the raging fire 80 miles southwest of Grand Isle.

Crew boats in the area rushed to the platform to fight the fire.

"There happened to be an offshore supply vessel on scene at the time," U.S. Coast Guard response coordinator Capt. Bryan Daley. "During the course of the event, three other offshore supply vessels contributed to the fire fighting."

The crew tried to extinguish the fire, but had to abandon the platform due to heavy smoke.

"There were four people on the platform," Daley said. "Our understanding is they entered a raft and the offshore vessel the Mary Wyatt Milano actually picked them up, delivered them to another platform."

The crew members were flown to Terrebonne General Medical Center in Houma.

A hospital spokeswoman said they were examined by doctors, treated and released.

The Coast Guard confirmed some oil got into the water a result of the fire.

"That oil appears to be residual oil that was already on the platform," Daley said. "The good news is that the source of the oil was secured immediately, so there's no danger of a free flowing well. But, there is some oil that was on board the platform and we're trying to assess how much of that oil actually entered the water."

The production platform, known as Ship Shoal 266 belongs to the Houston-based Renaissance Offshore, LLC.

The Coast Guard and Bureau of Safety and Environment Enforcement are now investigating the cause of the fire.

"Once they're able to get on board, they want to see the integrity of the rig and make sure it's safe," Daley said. "Then, they'll start examining, just like any other mishap, what happened. Are there gaps in our procedures? Are there gaps in the company procedures? What can we do to prevent this in the future?

According to the Coast Guard, as far as offshore platform fires go, this one went about a well as expected under the circumstances.

"From our standpoint, four lives weren't lost, four lives were saved," Daley said. "The oil was shut off. The fire was extinguished. The release to the environment was minimal. Those are all good points."