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Evacuations ordered near New Orleans as Isaac water threatens river lock

The Gulf Coast is struggling to recover from Hurricane Isaac as nearly 400,000 homes and businesses are without power. NBC's Gabe Gutierrez reports.

St. Tammany Parish, a community north of New Orleans on Lake Pontchartrain, on Saturday ordered the mandatory evacuation of thousands of residents in some 1,200 homes, fearing the failure of a lock along a canal could send a wave of water sweeping through neighborhoods.

Saturday night, parish emergency officials said that the opening of valves had relieved pressure on Lock 2 on the Pearl River Diversion Canal but the evacuation order would remain in place.

Earlier, parish officials said the order covered residents between Locks 1 and 2 on the Pearl River Diversion Canal. "Failure of Lock 2 is imminent," the parish said on its website.

The National Weather Service issued a flash flood warning until 4 a.m. ET Sunday.

The weather service said that if Lock and Dam No. 2 failed, the initial flood wave would be about 11 feet. It said the wave would take about one hour to travel the 11 miles downstream to Lock and Dam No. 1. 

Buses were sent to help with the evacuations in the area north of the city of Slidell.

The order came as hundreds of thousands of people in the region tried to clean up after widespread flooding by Isaac.

Some 360,000 homes and businesses were still without power.

A $15 billion upgrade to New Orleans' levee and pump system after Hurricane Katrina helped protect the city during Isaac, but areas outside were not as lucky.

Earlier this week, a levee in Plaquemines Parish overtopped, flooding dozens of homes and drowning at least two people.

The Weather Channel's Julie Martin takes a look at a slow-moving storm that is expected to dump heavy rain on the Midwest.

The flooding outside New Orleans led some local officials to wonder if the upgrades had pushed water into the outside areas.

Related: Isaac's rains hit Missouri, Illinois

The U.S. Army Corps of Engineers, responding to a request from Sen. David Vitter, R-La., said Saturday it would run models to see if that was the case, the New Orleans Times-Picayune reported.

David J. Phillip / AP

Ray Dumes, left, and his son Deron carry out a couch as they clean up their home in LaPlace, La., on Saturday.

Isaac's rains are now over the central U.S., helping ease the worst drought there in 50 years.

But high winds associated with the storm system were wreaking havoc. In Clay County, Ark., a possible tornado damaged two homes and hangars at the local airport.  

Mark Rockwell / Joe Jett

A hangar lies in ruins after high winds slammed the airport in Clay County, Ark.

Mark Rockwell / Joe Jett

Wind damage at the airport in Clay County, Ark.

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