Six people have been rescued and more are missing after a boat capsized off the Louisiana coast amid severe weather warnings.

The US Coast Guard said it received an emergency signal at around 4.30pm (local time) on Tuesday from a 129-foot commercial vessel, eight miles south of Port Fourchon in the Gulf of Mexico.

A widespread appeal for help was put out to nearby civilian boats and a coast guard vessel arrived on scene within 30 minutes.

A 154ft coast guard cutter boat rescued one person from the capsized boat, while a crew from the coast guard station at Grand Isle – 20 miles west of Port Fourchon – rescued another person.

A member of the crew of the Seacor Power is pulled from the sea
Image: A member of the crew is pulled from the sea. Pic: US Coast Guard

Civilian boats which joined the search efforts rescued four other people from the water, the coast guard said.

A large-scale rescue effort continued late into the night, rescuers added, with two cutters, two smaller vessels, a helicopter and an airplane deployed as part of the effort.

It is unclear how many more people may be missing.

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“We’re still searching for more people,” Petty Officer Jonathan Lally, a spokesman for the Coast Guard 8th District, told The New York Times.

The Times-Picayune reported that the vessel is used for oil and gas exploration, and Lafourche Parish President Archie Chaisson III confirmed to the outlet 18 people were on board before it capsized.

Severe storms hit Louisiana on Tuesday, with a flash flood warning in place for southeastern parts of the state and the National Weather Service predicting up to five inches of rain and winds of up to 50mph.