The mayor said Wednesday that Hurricane Katrina probably killed thousands of people in New Orleans.
The frightening estimate came as Army engineers struggled to plug New Orleans' breached levees with giant sandbags and concrete barriers, while authorities drew up plans to clear out the tens of thousands of people left in New Orleans and all but abandon the flooded-out city.
There will be a "total evacuation of the city. We have to. The city will not be functional for two or three months," Nagin said.
Most of those refugees _ 15,000 to 20,000 people _ were in the Superdome, which had become hot and stuffy, with broken toilets and nowhere for anyone to bathe. "It can no longer operate as a shelter of last resort," the mayor said.
Nagin estimated 50,000 to 100,000 people remained in New Orleans. He said 14,000 to 15,000 a day could be evacuated.
The Pentagon, meanwhile, began mounting one of the largest search-and-rescue operations in U.S. history, sending four Navy ships to the Gulf Coast with drinking water and other emergency supplies, along with the hospital ship USNS Comfort, search helicopters and elite SEAL water-rescue teams. American Red Cross workers from across the country converged on the devastated region in the agency's biggest-ever relief operation.
The death toll from Hurricane Katrina has reached at least 110 in Mississippi alone. But Louisiana has put aside the counting of the dead to concentrate on rescuing the living, many of whom were still trapped on rooftops and in attics.
A full day after New Orleans thought it had escaped Katrina's full fury, two levees broke and spilled water into the streets Tuesday, swamping an estimated 80 percent of the bowl-shaped, below-sea-level city, inundating miles and miles of homes and rendering much of New Orleans uninhabitable for weeks or months.
"We are looking at 12 to 16 weeks before people can come in," Nagin said on ABC's "Good Morning America, "and the other issue that's concerning me is we have dead bodies in the water. At some point in time the dead bodies are going to start to create a serious disease issue."
With the streets awash and looters brazenly cleaning out stores, authorities planned to move at least 25,000 of the New Orlean's storm refugees to the Houston Astrodome, 350 miles (560 kilometers) away, over two days in a vast convoy of some 475 buses.
Around midday, officials with the state and the Army Corps of Engineers said the water levels between the city and Lake Pontchartrain had equalized, and water had stopped rising in New Orleans, and even appeared to be falling, at least in some places. But the danger was far from over.
The Army Corps of Engineers said it planned to use heavy-duty Chinook helicopters to drop 20,000-pound (9,000-kilogram) sandbags Wednesday into the 500-foot (150-meter) gap in the failed floodwall. But the agency said it was having trouble getting the sandbags and dozens of 15-foot (4.5-meter) highway barriers to the site because the city's waterways were blocked by loose barges, boats and large debris.
Officials said they were also looking at a more audacious plan: finding a barge to plug the 500-foot (150-meter) hole.
As New Orleans descended deeper into chaos, hundreds of people wandered aimlessly up and down Interstate 10, pushing shopping carts, laundry racks, anything they could find to carry their belongings. Dozens of fishermen from up to 200 miles (320 kilometers) away floated in on caravans of boats to pull residents out of flooded neighborhoods.
On some of the few roads that were still passable, people waved at passing cars with empty water jugs, begging for relief. Hundreds of people appeared to have spent the night on a crippled highway.
In one east New orleans neighborhood, refugees were being loaded onto the backs of moving vans like cattle, and in one case emergency workers with a sledgehammer and an ax broke open the back of a mail truck and used it to ferry sick and elderly residents.
Police officers were asking residents to give up any guns they had before they boarded buses and trucks because police desperately needed the firepower: Some officers who had been stranded on the roof of a motel said they were being shot at overnight, AP reported.