An oil rig incident that sent 13 workers into the Gulf of Mexico was caused by a fire, not an explosion, the company that owns the rig said.

Mariner Energy said the cause of the fire on the platform still has not been found.

So far, no oil has leaked into the waters near Louisiana. The Coast Guard initially said a oil sheen had been spotted on the surface of the water, but crews were unable to find any spill.

Seven active production wells on the platform had been shut down shortly before the fire broke out.

All of the workers were rescued and one was taken to hospital.

The platform is located south of Vermilion Bay along the central Louisiana coast, just west of the BP rig that exploded earlier this year.

The explosion of the Deepwater Horizon oil rig on April 20 killed 11 workers and sent millions of litres of crude into the ocean.

It was nearly three months later before BP was able to say that the spill had stopped. No oil has emerged from the well since July 15.

Since April, costs of the spill have reached $8 billion, including $339 million in claims. BP says more than 28,000 people and 4,000 vessels are still engaged in responding to the spill.

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