With much of central New Orleans finally cleared of hurricane refugees, search teams widened operations Sunday to outlying streets, moving house to house with orders to evacuate all remaining residents from the city.

Determined to reestablish order, police shot several people and killed at least two after gunmen opened fire at or near a group of contractors traveling across a bridge on their way to make repairs, authorities said.

Mortuary teams also began the gruesome task of collecting corpses still floating in floodwaters, trapped inside buildings or abandoned on highways after the devastating storm that deluged the city a week ago. Officials warned that the death count -- which Louisiana officials put at 59 on Sunday -- is sure to rise exponentially.

"I think it's evident it's in the thousands," Health and Human Services Secretary Mike Leavitt said Sunday on CNN before he headed to the area, echoing predictions made last week by city and state officials.

Homeland Security Secretary Michael Chertoff said on "Fox News Sunday": "We need to prepare the country for what's coming."

"We are going to uncover people who died, maybe hiding in houses, you know, got caught by the flood -- people whose remains are going to be found in the street."

Louisiana officials again accused the Bush administration of being slow to respond to the flooding of New Orleans and then trying to shift the blame to state and local governments.

Chertoff, along with Defense Secretary Donald H. Rumsfeld and Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff, toured the storm-ravaged region, and Secretary of State Condoleezza visited Mobile, in her native state of Alabama. But at a news conference and in TV interviews, Chertoff declined to get drawn into discussions of the government's initial response efforts, trying instead to keep the focus on major challenges ahead.

Although some water has drained out of the city, a significant amount of New Orleans remains deep underwater. Officials predict that drainage operations will require weeks or months.

Many of the tourist sites in New Orleans appeared relatively unscathed. Sunday afternoon, a caretaker swept the leaves from in front of Cafe Du Monde, a city landmark. Elsewhere in the French Quarter, residents and shopkeepers tended to their buildings. The mansions along St. Charles Avenue in the Garden District showed little damage, most of it to trees.

Dan Packer, president and CEO of Entergy New Orleans, said Sunday afternoon that he expected to bring lights to at least parts of downtown by that night. "I feel confident that a part of the central business district will be lit up tonight and the rest tomorrow," he said. "As the city drains, we're going to get fixing."

Other parts of the city, including New Orleans East, Lakeview and the Ninth Ward, still lie submerged.

Episodes of looting, which peaked Wednesday, have dramatically diminished, as police and National Guard troops patrol the streets of the French Quarter and the business district. People raiding stores beyond the downtown appear to be focused on supermarkets and drugstores, where they can commandeer essential supplies.

Helicopter-borne rescue teams from the Army, Navy and Coast Guard expanded their range on Sunday, moving beyond the business district to drop supplies onto streets and fields, and to ferry people out.

"We're going to have to go house to house in this city," Chertoff said during a televised news conference in Louisiana. "We're going to have to check every single place to find people who may be alive and in need of assistance. This is not going to happen overnight."

It was difficult to determine how many residents remained in New Orleans, which had a population of about a half-million before Hurricane Katrina struck, or how long the rescue operation is likely to take. The thousands of people plucked from rooftops over the past week have constituted what officials say were the bulk of survivors. But the door-to-door task ahead could prove especially difficult.

A potential problem for authorities is people refusing to leave. Some residents say they want to protect their homes. Others fear the hassles of evacuation, particularly if they have pets, which are not allowed on the evacuation buses.

Saint Jones, 30, was on a stepladder Sunday morning readying the sign for the Bourbon Street strip club he manages and expressing a desire to stay. "This city will be back," he said. "It won't be that long."

Jim Gibeault, parked outdoors in an overstuffed recliner, has painted in black letters on a white sheet for helicopter pilots to see: "WITH HELP WE CAN HELP OURSELVES." At the Olde Nawlins Cookery, Mike Lala said the worst is over; he has no intention of leaving. "As soon as we get water and electricity, we're going to open up," Lala said, figuring business will boom with the arrival of "tens of thousands of construction workers."

Shawn Lazana, 36, an artist, and Kay Kennedy, 41, a writer, had been trying to stay in her uptown home when a military unit arrived with automatic weapons to evacuate them. Their street is flooded, and Lazana said he had seen the bodies of an elderly woman and a young child in the water. But they were trying to ride out the hard times so that Kennedy could continue to care for her cats, Armand and Gabriel. "We were basically forced out at gunpoint," Lazana said.

Chertoff confirmed that rescuers had encountered a significant number of people who have said they do not want to evacuate. But he made clear that everyone would need to leave, saying conditions would not be healthy for some time, nor can residents be assured of finding food or drinkable water.

"We are not going to be able to have people sitting in houses in the city of New Orleans for weeks and months while we de-water and clean this city," he said at the news conference.

"They're gonna have to leave," New Orleans Mayor Ray Nagin said. "The issue of life safety is really becoming a serious issue for me," citing the presence of toxins and bodies in the water. He said he expects that within three to four weeks, residents could come back to see their homes; but rebuilding and living in the city on a permanent basis likely cannot begin for another three to six months.

Eric Dryer, who works for the Harrods Creek, Ky., fire department, spent a tough day shepherding rescued New Orleans residents toward makeshift landing pads. "We're just trying to talk people into going," he said as he waited for three Navy helicopters to pick up 27 weary people.

"We tell them that every day, it's going to be harder and harder to get out of here because we're going to be farther away. Now it's a matter of sitting face to face with them and saying it's time to go," he went on. "If they don't go, people are going to be dying."

Initial reports about the bridge shooting were sketchy. John S. Rickey, spokesman for the Army Corps of Engineers Mississippi Valley Division, said 14 contractors with Boh Bros. Construction Co. were on the Danziger Bridge to retrieve heavy construction equipment. The contractors radioed to the Army Corp's emergency operations center for New Orleans that "they were taking fire," Rickey said. Local and state police responded to the scene and got the contractors out unharmed.

Marlon Defillo, spokesman for the New Orleans Police Department, said six people had been shot, with two dead.

At a shopping center on the north side of the bridge, people said they saw two men running down the bridge, exchanging fire with police. One of the men was caught; the other escaped into the deep floodwater.

"Shooting at the National Guard. Shooting at police. Shooting just to be shooting," Charles Hall said disgustedly. His friend Anthony Gilmore spat, "Innocents are suffering for their devilishness."

Across the street, watching the shootout were four men who had camped there for nearly a week. Twenty feet away lay the shrouded body of a man who had suffered a seizure on Wednesday. His dog still sat by his side, barking at anyone who came near. There was no one to remove the body, and nowhere to take it.

In some areas of New Orleans relatively unaffected by flooding, such as the Garden District and farther out St. Charles Avenue, dozens of people could be seen outside Sunday afternoon, wheeling shopping carts down the street. Many had heard that a supply truck was coming by. At the corner of St. Charles and Napoleon Avenue, soldiers handed out cartons of bottled water.

Several residents said they would leave if the evacuation process promises not to be too miserable. Others said they had been willing to leave, but could only get out now because they were afraid of what was going on outside.

James Bills, 42, a graphic designer and filmmaker, stayed at a downtown Best Western with his wife and two children through the hurricane. Afterward, he said armed gangs patrolled the streets. The hotel manager's husband, who had a shotgun, gave him a 9mm handgun.

"Here I am, a 42-year-old father of two, hiding behind a steel pole and pointing a pistol at people outside," he said. "Everyone said if you leave right now, they'll rob you and take your vehicle."

"It was like Baghdad, only with floods," said Gabriel Whitfield, the hotel manager's husband. "I couldn't believe I was standing on American soil."

Nodding toward Whitfield, Bills said, "He was the law on the block before the military got here."

Because they only had one day of supplies and children to feed, the two said they looted the local Wal-Mart with police permission. By Sunday afternoon, it appeared that all was clear. For the first time in a week, Bills allowed his 2-year-old daughter outside. He was sitting on a curb with her on his lap.

"It's a lot quieter now," he said. "We can get out of here now."

Staff writer Bradley Graham in Washington contributed to this report.

Rescuers bring to shore in uptown New Orleans victims of the flooding that resulted from Hurricane Katrina. Helicopter-borne rescue teams from the Army, Navy and Coast Guard expanded their range yesterday, moving beyond the business district. On Interstate 10, a woman is in tears -- sad and frustrated, she said, because she has been unable to locate her mother. Officials said thousands remain to be evacuated in New Orleans.Stranded automobiles line a flooded roadway in New Orleans. Although city and federal officials have said all residents must leave, some are refusing. Some business owners in tourist areas that were relatively unscathed by Hurricane Katrina say they will reopen soon.A makeshift burial site was rapidly put together for a woman whose body had been lying on the streets of downtown New Orleans for several days. It reads: "Here Lies Vera, God Help Us." The official death tally for Louisiana stands at 59 but is expected to rise much higher.A man clings to the top of a vehicle before being rescued by the Coast Guard from a flooded street in New Orleans. Draining all flooded city streets is expected to take weeks or months.