The bodies of 45 patients left in a hasty evacuation were recovered from a New Orleans hospital, officials said Monday, as the city braced for the scenes left by the receding waters.

The news of the grim recovery at the Memorial Medical Center, the largest such discovery since Hurricane Katrina struck, came hours after President Bush completed a tour of parts of the city and spoke to local officials. He defended his administration's record, even as the chief of the federal emergency agency, Michael D. Brown, said in Washington that he was resigning after being yanked off the hurricane relief job three days ago.

Bush said that he will name R. David Paulison, now U.S. fire administrator and director of preparedness for FEMA, to lead the agency. A poll showed that Bush's standing reached a new low and that a majority of Americans disapprove of his response to Katrina.

Wrapping up his two-day visit, Bush saw a city trying to struggle back to life. But while the higher and drier downtown area buzzed with the sounds of generators and cleanup, vast swaths of the city remained a devastated frieze of dried mud, broken homes and foul stench.

Officials said the bodies found Sunday in the Memorial Medical Center were left there after a frantic evacuation, days after the storm passed and floodwaters began to rise. An official of the hospital owners said the patients died before the evacuation and their bodies were left in the facility.

But the discovery was certain to raise new questions about why so many city hospitals were not evacuated before the storm. Two medical professionals inside the Memorial Medical Center said conditions began to turn desperate shortly after the floodwaters cut off roads. The darkened corridors were jammed with families. Drinking water grew scarce. Medical supplies exhausted quickly; even IVs were being rationed, they said.

"Things looked like they were going downhill quickly," said Scot Sonnier, an oncologist there. He left before the evacuation, thinking other doctors were handling it, he said.

The city braced for more grim discoveries as the receding waters allowed search parties to reach isolated buildings. But the death toll -- 279 for Louisiana -- was still far below the initial prediction of the city's mayor that 10,000 perished.

"It's hot. It smells. But most of the houses we are looking at are empty," Oregon National Guard Staff Sgt. James Lindseth, 33, said as his platoon, inspecting for people dead or alive, worked its way through dank and broken homes that had been in the water a few days ago.

In New Orleans's downtown, most of it on higher and drier land, authorities allowed business owners to check their buildings Monday. Dump trucks with claws plucked the growing piles of debris from street corners and the air rumbled with the sound of generators.

"The least we can do is clean up our own streets," Wallace Kimbrough, 43, said as he pried debris out of the storm drain beside his home in the French Quarter. "Hey," he exclaimed, holding up a plastic bag he pulled from the muck. "Somebody lost their marijuana seeds."

In some of the outlying parishes, local school boards announced plans to restart classes next month. Louis Armstrong New Orleans International Airport said it will begin operating commercial flights on Tuesday, joining the traffic of helicopters, cargo planes and private charters bringing relief supplies.

Roy A. Williams, the airport's director of aviation, said the rush of evacuees has ended, and Delta, Continental and Northwest have said they want to resume flights to their hub cities.

But just outside downtown, large swaths of New Orleans remained lifeless and still. The growing concert of working pumps had brought the flood down to less than half the city by Monday, although water was seeping through a previously repaired levee. Brig. Gen. Doug Pritt of the Oregon National Guard described it as a minor leak, the Associated Press said. But areas that emerged from the muck remained images of devastation.

There, the homes were draped with trees plucked and flung by the storm. Cars lay overturned; appliances have been ripped from their moorings and thrown onto streets and bridges. The retreating water shone multicolored with oil, and when disturbed, released an overwhelming stench. The air smelled of rot and decay.

Officials of St. Bernard Parish, a poor, racially mixed area east of downtown, told residents in a meeting in Baton Rouge that the homes there would likely not be habitable for four months. Just north of that parish, near the Lakefront Airport, Gene Giroir, 65, pried open the front of his hardware store for the first time in two weeks. The contents lay in a dark, soggy ooze on the floor.

"The only thing left were things hanging on the wall above four feet. That's how high the water got," he said.

He owned the store with his brother and brother-in-law. "This was our living. I've been here since 1949. I grew up in this business, and I don't know whether I want to do it all again," he said.

The president's visit caused little wake on the streets. Many workers and residents said they had only vaguely heard he was coming. Several shrugged. Most said they were too busy or preoccupied to care.

While Bush was traveling, Brown's resignation was announced in Washington. Brown had become the focus of anger for the slow federal mobilization after the storm savaged the Gulf Coast two weeks ago, unleashing a flood that engulfed most of New Orleans and flattening entire communities in Mississippi and Alabama.

In a written statement, Brown said he told Bush that it is "important that I leave now to avoid further distraction from the ongoing mission of FEMA." Homeland Security Secretary Michael Chertoff said he will name a permanent deputy director at FEMA, a new position for the agency.

Brown's departure was greeted with glee by Democrats. "Mike Brown's decision to resign from FEMA is the best decision he's made in three weeks," said Democratic National Committee Chairman Howard Dean.

The announcement of the grim find of bodies at Memorial Medical Center came after the president had left New Orleans.

The hospital, located in the center of the city, had fared the storm pretty well, said Sonnier, who rode out the hurricane at the hospital with his fiancee, Zoe Larner, a hematologist. But after the storm passed and news came of a broken levee, Sonnier said things became grim. Medical supplies were dwindling quickly, and the hospital's emergency power left the hallways dim. The hospital hallways were crowded with families of patients and staff, and soon came reports of looting and lawlessness, he said.

"Things looked like they were going down quickly," he said.

After two days, he waded to his nearby house, where Larner was listening to reports to evacuate the city, Sonnier said he did not know whether he could get back to the hospital, and he believed there was an emergency team of doctors to care for the patients. "I had a feeling things were going bad, and the best thing to do was get out of town," he said. Shortly after, he said, the hospital was evacuated.

Bob Johannesen, a spokesman for the state Department of Health and Hospitals, said the bodies of 45 patients were recovered from the hospital Sunday, although Dave Goodson, an assistant administrator, said the toll was 57, according to the AP.

"These patients were not abandoned," Goodson said. He said they had died before the evacuation. A spokesman for Tenent Healthcare Corp., which owns the hospital, told the AP that some of the people found Sunday had died before the storm, and the others died before the evacuation, which other officials said was done by boats. Many of the patients were in long-term acute care for people with serious ailments, he said.

Several medical care facilities became the site of chaos as the floods rose, with reports of looting and holdups for drugs inside the hospitals. One facility had to post a police sniper on the roof to keep order.

Sonnier said he assumed the emergency team of physicians left in the hospital would carry out the evacuation. But in an interview outside the eight-story brick facility, he said, "I will always have well, not regrets, but concerns over whether I did the right thing."