As federal and local officials argued about when residents should be permitted to return to this evacuated city, hundreds of people have ignored orders to keep out and found their way past scattered armed checkpoints to reoccupy their homes.

Dozens of residents could be seen out walking dogs, raking leaves or repairing homes this weekend in those neighborhoods least affected by Hurricane Katrina's devastation -- Uptown, the Garden District and Algiers.

"People call and ask me, 'How did you get in there?' and I say, 'I drove!' " said Linda Brett, 53, a real estate agent and resident of Algiers Point who was outside a friend's house Sunday afternoon.

The outlook was much bleaker in sections such as New Orleans East and the Lower Ninth Ward, which suffered heavy flooding. Many streets were still covered in mud and debris, and several were impassable. Some were blocked by fallen trees or by houses that had floated off their foundations. Police checkpoints also were stricter.

FEMA's urban search-and-rescue teams continued to canvass these areas and turned up several corpses -- and one survivor on Sunday. About 1:30 p.m., an Oregon National Guardsman indicated he had heard someone inside one home. He had been leaving food for the dog at the home, but on Sunday he heard a voice. After breaking inside, rescuers found a disoriented man, identified as Reyne Johnson, 39, and his dog. "He was living in a dark, small, wet efficiency," said Louie Fernandez, a FEMA spokesman. "He seemed unaware of his surroundings."

The death toll on Sunday stood at 646 in Louisiana and 218 in Mississippi.

The unofficial arrival of people to this city takes place as Mayor C. Ray Nagin and Vice Adm. Thad W. Allen, head of the federal relief effort, differ starkly over the state of health and security in the city.

Nagin has set a schedule for more than 180,000 people to return to city neighborhoods in the coming weeks, beginning Monday with the section known as Algiers, across the Mississippi River from the downtown. But Allen said that New Orleans is not safe and that he will strongly urge Nagin to reconsider that schedule, citing the possibility of additional flooding, security issues and disease.

Many residents have already arrived. In Algiers on Sunday, worshipers gathered for Mass at Holy Name of Mary Catholic Church. At the river's edge, dozens turned up for groceries distributed by troops. Residents there say they have power, water and even cable TV. Many stoplights do not work, however, and a truck collided with an ambulance at one of the main intersections in Algiers.

"We didn't come back -- we stayed here the whole time," said Ann Ruiz, one of Brett's neighbors.

Down the street, at the Mardi Gras float empire of Blaine Kern, also known as "Mr. Mardi Gras," a few employees were back at work. Brenda Carter, a prop artist, was painting a gondolier sculpture for a float. Kern, who has about 20 warehouses in Algiers for the floats and sculptures, said he will be ready for Mardi Gras.

"Come back in here tomorrow and I'll have 30 to 50 workers in here," Kern said, standing in a warehouse stocked to the rafters with witches, princes and imaginary creatures.

But even in those parts of New Orleans where businesses have been invited to return, many are still shuttered. Franco Valobra, owner of a jewelry and antiques shop, is among those few store owners who seem ready to go. The electricity is back at his store on Royal Street, and he was planning to open on Monday. His employees are scattered upstate, but he plans to put them up in hotel rooms.

"People say, 'Where are you going to have customers? There's no one here,' " Valobra said. "[W]e need to show people we're back."

For now, plans call for the return of people to begin, at least officially, on Monday, though that could still change. Allen said that he hopes to sit down with Nagin on Monday and "have a very frank conversation," and develop a plan for allowing residents back into the city.

Responding to continuing criticism of FEMA, Allen said the dispersion of evacuees has made the agency's job more difficult. "Previous natural disasters . . . have been concentrated in a geographical area. Trying to get out and find everybody that was evacuated and where they went, to offer them individual assistance, is a challenge," he told CBS's "Face the Nation."

Throughout the region hit by Hurricane Katrina, people have reported that they could not reach anyone with FEMA or the Red Cross.

In Wiggins, Miss., about 30 miles from the coast, Louise Deisenroth and five neighbors who lost their homes were preparing for another day in line in hopes of getting financial assistance from the Red Cross. They spent much of last week in long lines in four towns without getting an interview.

"It looks like nobody wants to help anybody in Wiggins," she said Sunday. Some local friends who evacuated to Tennessee got assistance right away, she said. "It looks like if you go out of state, you can get help, but you can't get help in the disaster area."

Deisenroth and the five neighbors sharing her mobile home plan to travel 30 miles to Hattiesburg, Miss., on Monday to seek Red Cross assistance.

In other cases, patience and luck paid off. Steve Lecourt, whose family was left homeless after the hurricane, said he had finally gotten through to FEMA on a friend's cell phone Friday after trying for a week and got an interview with the Red Cross as well.

"I did get some help from the Red Cross and they are supposed to be mailing me a check," he said Sunday. "I did get a hold of FEMA, and they are supposed to be sending me a package. . . . I guess we have to be more patient than what we expected."

Staff writer Susan Schmidt in Washington contributed to this report.

Jim Baker sweeps up after the slight damage his home received from Katrina in the historic district of Algiers Point. Baker said he evacuated to Baton Rouge and came home Saturday.