NEW ORLEANS - Louisiana and Mississippi officials conducted search-and-rescue missions Wednesday for residents stranded by Tropical Storm Isaac, which flooded highways and homes and pushed water over the top of a vital levee.
While Isaac lost its hurricane status Wednesday afternoon, officials warned of continued life-threatening hazards from storm surges and local flooding.
The situation was particularly dire in Plaquemines Parish, southeast of New Orleans, where 3,000 people remained in one area close to an 8-foot tall levee that waters are threatening, according to a release from Louisiana Gov. Bobby Jindal's office.
Earlier Jindal said a first estimate from local officials in the parish showed as many as 800 homes may have received significant water damage. The U.S. Army Corps of Engineers reported significant storm surge in the parish, scene of many rescues.
One involved National Guard troops who moved 112 residents from the Riverbend nursing home to another facility.
Dozens of Louisiana families that had ignored mandatory evacuation orders in a low-lying area retreated to their attics and roofs and sought rescue amid the howling wind and pounding rain.
Mississippi Gov. Phil Bryant said Wednesday that 34 people were rescued by boat in Hancock County, on the coast northeast of New Orleans, and 15 others were picked up by National Guard troops in trucks. CNN affiliate WWL reported major flooding in LaPlace, west of New Orleans.
Isaac threatened to keep churning over the region for another day.
The punishing storm conditions will persist "all day today, into tonight, into tomorrow," said Richard Knabb, director of the National Hurricane Center.
The region's largest power provider, meanwhile, told customers to prepare for "extended power outages." Overall, power companies said more than 817,000 customers were without power in Louisiana, Mississippi, Alabama, Florida, Texas and Arkansas. More than three-fourths of the outages were in Louisiana.
Sixty road segments in Louisiana were closed as of Wednesday afternoon, officials said, including the Lake Pontchartrain Causeway.
"We are trying to keep priority routes open as much as safely possible," said spokeswoman Amber Leach of the Louisiana Department of Transportation and Development.
As of 4 p.m. CT, Isaac's maximum sustained winds were at 70 mph -- below the hurricane threshold of 74 mph.
The storm's center was about 35 miles south of Baton Rouge and about 60 miles west of New Orleans, the hurricane agency said. Police officers said the city will be under a dusk-to-dawn curfew beginning Wednesday evening.
Isaac was creeping to the northwest at only 6 mph, giving it a long time to inflict damage.
Jindal said there was a report of a fatality in a fire early Wednesday, but officials had not confirmed the report.
Officials were quick to emphasize that the huge federal investments in recent years to avoid a repeat of Hurricane Katrina's horror had worked in New Orleans.
"The system that the country invested in is absolutely paying off," said Louisiana Sen. Mary Landrieu.
"There is no evidence of any (water) overtopping (canals)" in the city, said the senator's brother, New Orleans Mayor Mitch Landrieu. "We have full confidence the levees will hold."
But in Plaquemines Parish, just southeast of the city, three levees overtopped, creating a kind of flooding the parish did not see even during Hurricane Katrina, which hit seven years ago Wednesday.
More than 150 calls came in to 911 from people wanting to be rescued, said Terry Rutherford, commander of authorities in Plaquemines Parish.
By mid-morning, 75 people had been rescued from flooded homes and rooftops in Braithwaite in the parish, WWL reported. At least 25 others were awaiting rescue on the parish's east bank, the report said, citing parish President Billy Nungesser.
Emergency management officials reported the overtopping of an 18-mile stretch of the back levee from Braithwaite to White Ditch, according to the National Weather Service office in New Orleans.
The levee is maintained by the parish and has not been part of the federal hurricane protection levee system, according to officials.
Katrina breached the levee in two places, the Army Corps of Engineers said.
"It's very unfortunate that people did not heed the warnings," Mary Landrieu told CNN, adding, "our hearts go out" to them.
"Now the Coast Guard's got to go out with winds still gusting 60 to 70 mph in some areas" to save them, she said.
The New Orleans levee system and pump stations were working furiously to deal with the deluge.
The system was rebuilt and reinforced at a cost of $14 billion after it failed when Katrina struck in 2005. Nearly 1,800 people died as a result of that storm, the majority when levees and flood walls failed and flooded.
Landrieu said she was among some officials who had pushed for Plaquemines Parish to be included in the federally funded projects, but the corps follows a formula "based on economic impact" that leaves out