Louisiana and Mississippi officials conducted search-and-rescue missions Wednesday for residents stranded by slow-moving Tropical Storm Isaac, which flooded homes and pushed water over the top of several levees.

While Isaac lost its hurricane status Wednesday afternoon, officials warned of continued life-threatening hazards from storm surges and local flooding.

The surge was unusually bad in LaPlace, about 25 miles northwest of New Orleans, where many people had been rescued or still needed to escape rapidly rising water, said Paige Falgoust, communications director for St. John the Baptist Parish.

"We have established pickup points in certain subdivisions that are easy access for our residents to get to by foot," she said.

People were being taken to a processing center at a church then bused to state shelters outside the parish.

The storm surge from Lake Ponchartrain came quickly and "in a different way from what we were expecting," Falgoust said.

"In some areas the water levels rose in 10 minutes to where they could not get out of their homes," she said.

According to a release from Louisiana Gov. Bobby Jindal's office, 1,500 people had been evacuated with 1,500 more needing rescue. The state sent 89 buses to take evacuees to shelters.

The situation also 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, the governor's office said.

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.

CNN iReporter Kayla Robin, who took photos of the Braithwaite flooding and rescue arrivals, said the experience was horrific.

"When they got in, you could tell they were in shock and weren't expecting this," she told CNN.

Robin, 20, lives in Caernarvon in St. Bernard Parish, right next to Braithwaite. She lives to the east of a floodgate that protected St. Bernard from the floodwater.

Robin said there was no water in her home, although there was calf-high water in the streets.

"It was traumatic going to the wall and seeing both sides at one time," said Robin of the contrasting situations. "Thankfully, we have everything -- but these people (on the other side) are reliving Katrina seven years later."

Meanwhile, officials said there were 12 incidents of looting. New Orleans Police said arrests were made in each case, but didn't specify how many people were involved.

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 834,000 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 10 p.m. CT, Isaac's maximum sustained winds were at 60 mph.