More than 500,000 people have lost power as Hurricane Isaac moves through south-east Louisiana bringing torrential rain and flooding.
New Orleans is being hit with 80 mile-per-hour winds.
It comes 7 years to the day after the devastation caused by Hurricane Katrina.
Some residents are believed to be trapped after a flood wall was breached.
The multibillion-dollar barriers were built to protect the city after 2005 disaster.
The slow-moving but powerful Category 1 hurricane was felt along the Gulf Coast.
It is threatening to flood towns in Mississippi and Louisiana with storm surges of up to 12 feet and top sustained winds up to 120 kph.
Police and National Guard units have been patrolling the virtually empty downtown of the port city.
However authorities reported no security problems.
Reporter Greg Milam is there.
He says the situation is pretty grim.
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