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FILE - ARCHIVED PHOTO-This image provided by NASA shows sediments in the Gulf of Mexico taken by the Aqua satellite in Sept. 2002. (AP Photo/NASA)

The Coast Guard says it is responding to a "loss of well control event" at an oil and gas platform 74 miles southwest of Port Fourchon, La., in the Gulf of Mexico.

, an energy news resource supported by writers from the Houston Chronicle, the "decades-old" well had been inactive for 15 years, and on Tuesday was said to be " leaking slowly with relatively few hydrocarbons."

Energy Resources Technology Gulf of Mexico LLC reported the event, saying that a 4 mile-by-.75 mile "rainbow sheen" was visible in the gulf via flyover.

"It is actively leaking natural gas," Coast Guard spokesman Jonathan Lally confirmed to NBC News on Tuesday night.

The well, about 74 miles off Port Fourchon, La., is owned by Energy Resources Technology Gulf of Mexico, a subsidiary of Talos Energy.

, the Houston, Texas-based Talos said the gas is coming from a well that it was in the process of abandoning. The leak happened while it was trying to permanently plug the well.

"We expect that the well will be shut in within the next 24 hours," Talos said in a statement Tuesday.

All platform personnel were evacuated safely, and the Coast Guard is working with the Bureau of Safety and Environmental Enforcement to investigate the occurrence, a release said.

According to the CNN report, the well leaked about six barrels, or 252 gallons of oil, in addition to the gas, the company said. The oil is expected to evaporate quickly, according to the company.

A member of the Gulf Restoration Network in New Orleans told CNN that the leak did pose a threat to marine life in the area.

This story has developed over time. The original story was based on a news release issued by the Coast Guard around 4 p.m. Tuesday. Near midnight, additional information was added based on reporting from NBC News and CNN. On Wednesday morning, reporting from Fuel Fix, an energy news blog associated with the Houston Chronicle, was incorporated into the story.