No civilians in New Orleans will be allowed to carry pistols, shotguns or other firearms, said P. Edwin Compass III, the superintendent of police. "Only law enforcement are allowed to have weapons," he said.

But that order apparently does not apply to hundreds of security guards hired by businesses and some wealthy individuals to protect property. The guards, employees of private security companies like Blackwater, openly carry M-16's and other assault rifles. Mr. Compass said that he was aware of the private guards, but that the police had no plans to make them give up their weapons.

Nearly two weeks after the floods began, New Orleans has turned into an armed camp, patrolled by thousands of local, state, and federal law enforcement officers, as well as National Guard troops and active-duty soldiers. While armed looters roamed unchecked last week, the city is now calm. No arrests were made on Wednesday night or this morning, and the police received only 10 calls for service, a police spokesman said.

The city's slow recovery is continuing on other fronts as well, local officials said at a news conference. Pumping stations are now operating across much of the city, and many taps and fire hydrants have water pressure. Tests have shown no evidence of cholera or other dangerous diseases in flooded areas, though health officials have said the waters contain unsafe levels of E. coli bacteria and lead.

Efforts to recover corpses have also started.

But there were still signs of confusion and uncertainty over government plans. FEMA's director, Michael D. Brown, had said his agency would begin issuing debit cards, worth at least $2,000 each, to allow hurricane victims to buy supplies for immediate needs. More than 319,000 people have already applied for federal disaster relief, and many evacuees began lining up at the Astrodome, in Houston, early today in hope of getting cards.

"The concept is to get them some cash in hand," Mr. Brown had said, "which allows them, empowers them, to make their own decisions about what they need to have to restart their lives."

But this afternoon, FEMA announced that it no longer planned to issue the cards. An agency spokesman, David G. Passey, said that he did not know why the program was scrapped but that now "we believe that our normal methods of delivery - checks and electronic funds transfer - will suffice."

In Washington, the House an Senate overwhelmingly approved $51.8 billion for relief efforts, the second disbursement since the storm devastated the Gulf Coast on Aug. 29. The funds include $50 billion for FEMA, $1.4 billion for the Department of Defense and an additional $400 million for the Army Corps of Engineers. The request follows a $10.5 billion package that President Bush signed on Friday and that is intended to address the immediate needs of survivors.

Hundreds of miles to the east, Ophelia, a tropical storm off the Florida coast, was upgraded to hurricane status this afternoon after its winds reached speeds of 75 miles per hour. Forecasters have predicted that Ophelia will turn east into the Atlantic Ocean during the next few days, although its path remains unclear.

With pumps running and the weather here remaining hot and dry, water has receded across much of New Orleans. Formerly flooded streets are now passable, although covered with leaves, tree branches and mud.

A spokesman for the Army Corps of Engineers, Dan Hitchings, said 37 of the city's 174 permanent pumps were working this afternoon, removing about 11,000 cubic feet of flood water per second. The city's 174 pumps have the capacity to remove about 81,000 cubic feet of water each second when they are all operational.

While Mr. Hitchings would not try to quantify how much the water level in the city had dropped, he did say that "it's going down."

The Army Corps of Engineers continues to try to plug two levee breaks, Mr. Hitchings said, on London Avenue, and at the end of the Harbor Navigation Canal.

Many neighborhoods in the northern half of New Orleans remain under 10 feet of water, and Mr. Compass said today that the city's plans for a forced evacuation remained in effect because of the danger of disease and fires.

Mr. Compass said he could not disclose when New Orleans residents might be forced to leave en masse, but other police officers and law enforcement officials said the city planned to start as early as tonight.

The city's Police Department and federal law enforcement officers from agencies like the United States Marshals Service will lead the evacuation, Mr. Compass said. Officers will search houses in both dry and flooded neighborhoods, and no one will be allowed to stay, he said.

Many of the residents still in the city said they did not understand why the city remained intent on forcing them out.

"I know the risks," said Renee de Pontchieux, as she sat on a stool outside Kajun's Pub in the working-class Bywater neighborhood east of downtown. "We used to think we lived in America - now we're not so sure. Why should we allow this government to chase us out and allow people from outside to rebuild our homes? We want to rebuild our homes."

But Ms. De Pontchieux said she was resigned to being evacuated if the police insisted. "It would be foolish" to fight, she said.

This afternoon, President Bush announced a series of measures intended to make it easier for evacuees to receive state and federal assistance, like Medicaid and food stamps, to make the aid as "simple as possible to collect."

"There will be many difficult days ahead, especially as we recover those who did not survive the storm," he said, adding that he was declaring Sept. 16, next Friday, a National Day of Prayer and Remembrance.

Vice President Dick Cheney, accompanied by Attorney General Alberto Gonzales and the secretary of homeland security, Michael Chertoff, surveyed damaged neighborhoods in the Gulf Coast region today, and pledged that the federal government would help rebuild the devastated area.

Mr. Cheney visited Gulfport, Miss., and New Orleans, where flood waters are growing increasingly fetid and thousands of people are still insisting on staying, despite the evacuation order.

"The president asked me to come down to take a look at things, and to begin to focus on the longer term, in terms of making certain obviously that we're getting the search-and-rescue missions done and all those other immediate things," Mr. Cheney said after touring a neighborhood in Gulfport. "The progress we're making is significant."

Mr. Cheney's visit follows a visit earlier this week by President Bush, his second since the storm hit, following much criticism last week that the administration and federal agencies had been slow in responding to the disaster.

An estimated 5,000 to 10,000 people remain inside New Orleans more than a week after Hurricane Katrina hit, many in neighborhoods that are on high ground near the Mississippi River.

But the number of dead still remained a looming and disturbing question.

In the first indication of how many deaths Louisiana alone might expect, a spokesman for the State Department of Health and Hospitals, Robert Johannessen, said on Wednesday that the Federal Emergency Management Agency had ordered 25,000 body bags. The official death toll remains under 100.

In Washington, House and Senate leaders announced a joint investigation into the government's response to the crisis. "Americans deserve answers," said a statement by the two top-ranking Republicans, Speaker J. Dennis Hastert and Senator Bill Frist, the majority leader. "We must do all we can to learn from this tragedy, improve the system and protect all of our citizens."

Democratic leaders, however, said they would not participate, citing a preference for an independent inquiry.

The government continued its efforts to help evacuees. At the Astrodome in Houston, where an estimated 15,000 New Orleans evacuees found shelter over the weekend, the number had dwindled to only about 3,000 on Wednesday as people were rapidly placed in apartments, volunteers' homes and hotels that had been promised reimbursement by FEMA.

With the overall death toll highly uncertain, Mr. Brown, the FEMA director, said in Baton Rouge that the formal house-to-house search for bodies had begun at midmorning. He said the temporary mortuary set up in St. Gabriel, La., was prepared to receive 500 to 1,000 bodies a day, with refrigeration trucks on site to hold the corpses.

"They will be processed as rapidly as possible," Mr. Brown said.

As it worked to remove the water inundating the city, the Corps of Engineers said that one additional pumping station, No. 6, at the head of the 17th Street Canal, had started up, and that about 10 percent of the city's total pumping capacity was in operation. But the corps added that it was dealing with a new problem: how to prevent corpses from being sucked to the grates at the pump inlets.

"We're expending every effort to try to ensure that we protect the integrity of remains as we get this water out of the city," said John S. Rickey, chief of public affairs for the corps. "We're taking this very personally. This is a very deep emotional aspect of our work down there."

Officials emphasized that as testing of the flood waters continued, substances in addition to E. coli bacteria and lead were likely to be found at harmful levels, especially from water taken near industrial sites.

"Human contact with the floodwater should be avoided as much as possible," the environmental agency's administrator, Stephen L. Johnson, said.

A spokesman for the federal Centers for Disease Control and Prevention said state and local officials had reported three deaths in Mississippi and one in Texas from exposure to Vibrio vulnificus, a choleralike bacterium found in salt water, which poses special risks for people with chronic liver problems.

At a news conference this morning, officials in New Orleans cautioned people to decontaminate themselves as best as possible when entering homes after wading through the floodwater.

Among the authorities, though, some confusion lingered about how a widespread evacuation by force would work, and how much support it would get at the federal and state level. Mayor C. Ray Nagin told the police and the military on Tuesday to remove all residents for their own safety, and on Wednesday, the police superintendent, Mr. Compass, said state laws give the mayor the authority to declare martial law and order the evacuations.

"There's a martial law declaration in place that gives us legal authority for mandatory evacuations," Mr. Compass said. "We'll use the minimum amount of force necessary."

But because the New Orleans Police Department has only about 1,000 working officers, the city is largely in the hands of National Guard troops and active-duty soldiers.

State officials said Gov. Kathleen Babineaux Blanco could tell the Guard to carry out the forced removals, but they stopped short of a commitment to do so. In Washington, Lt. Gen. Joseph R. Inge, deputy commander of the United States Northern Command, said regular troops "would not be used" in any forced evacuation.

The state disaster law does not supersede either the state or federal Constitutions, said Kenneth M. Murchison, a law professor at Louisiana State University. But even so, Mr. Nagin's decision could be a smart strategy that does not violate fundamental rights, Professor Murchison said.

When police officers came to Billie Moore's 3,000 square foot Victorian to warn her of the health risks of remaining in the city, she pushed her identification tag from the hospital where she works as a nurse through slats in the door.

"I guess you know the health risks then," the officer said as he walked away.

Ms. Moore and her husband, Richard Robinson, who do not drive and use bicycles for the 5-mile ride to their jobs at the still-functioning Ochsner Hospital in suburban Jefferson Parish, have no plans to leave. Their circa-1895 home, on the city's southwest flank, suffered virtually no damage in the hurricane or its aftermath. They have been lighting an old gas stove with a match to cook pasta and rice, dumping cans of peas on top for flavor.

"We try to be normal and sit down and eat," Ms. Moore, 52, explained as she showed off the expansive, well-kept home where they have lived for 10 years. "I think that's how we'll stay healthy is if I keep the house clean."

Ms. Moore said she had not worked since the hurricane because there are few babies left at the hospital, but that she remains on standby; her husband has been on duty the past five days.

"I don't want to go, I don't want to lose my job," she said. "Who's going to take care of the patients if all the nurses go away?"

Alex Berenson reported from New Orleans for this article, and Timothy Williams from New York. Reporting was contributed by John Broder from New Orleans, Sewell Chan from Baton Rouge, La; Christine Hauser from New York, and Matthew L. Wald from Vicksburg, Miss.