NEW ORLEANS -- Rescue teams searched swamped street after street, house to house yesterday for those still living in this devastated city, as the U.S. health and human services secretary estimated that Hurricane Katrina and the flood that followed killed thousands.

The magnitude of the total loss has so far only been hinted at by the sight of bodies lying in city streets and floating in brown waters, and by reports of survivors too elderly, frail or ill to leave their homes. While some survivors continued to resist evacuation by troopers, police and the Coast Guard scouring neighborhoods by helicopter, boat and truck, one official of a neighboring parish broke into tears on television pleading for just this kind of help.

"I'm sick of the press conferences," cried Aaron Broussard, president of Jefferson Parish, just west of New Orleans, on NBC's Meet the Press. "For God's sake, shut up and send us somebody."

Federal officials, variously defensive or resolute about the relief effort, began preparing Americans for the horrors of the weeks ahead.

On Day 7 of the hurricane's aftermath, HHS Secretary Michael Leavitt emerged as the first federal official to estimate the storm's toll in human life on the Gulf Coast.

"I think it's evident it's in the thousands," Leavitt told CNN. "It's clear to me that this has been a sickeningly difficult and profoundly tragic circumstance."

Homeland Security Secretary Michael Chertoff told Fox News Sunday that when New Orleans and other flooded areas are drained of water, the disaster's most dreadful consequences will be revealed.

"We need to prepare the country for what's coming," Chertoff said. "We are going to uncover people who died hiding in the houses, maybe got caught in floods; it is going to be as ugly a scene as you can imagine."

It was not clear yesterday how many people remained in New Orleans. The people who massed in great numbers awaiting help on elevated highways and at the Superdome and the convention center had been ushered out in the stepped-up relief effort Friday and Saturday.

At Louis Armstrong International Airport, which was turned into a field hospital and evacuation staging area, most of some 8,000 people who had been there Friday and Saturday had left by yesterday for shelters in Texas, Arkansas, Florida and other states.

National Guard and Coast Guard helicopters continued ferrying survivors all day from the city to the airport. The troops had painted a neon orange helicopter landing zone on at least one elevated section of Interstate 10, using it as a pickup point for survivors brought in by small boats and rafts from flooded neighborhoods.

Rescue crew members said they visited some houses three times, trying to convince people that it was time for them to leave the city. In some cases, the survivors chose to stay.

"Phase two of our job may be harder than phase one," Army Lt. Gen. Russel Honore told CNN, referring to the work of finding remaining survivors. Honore is stationed in New Orleans, leading the military effort, which is expected to involve more than 50,000 active-duty and National Guard troops arrayed along the Gulf Coast, chiefly in Louisiana and Mississippi.

Despite the heavy military presence, there was more violence in New Orleans yesterday. New Orleans police officers shot and killed four people and wounded two others who had fired at officers escorting a convoy of contractors across a bridge yesterday morning, The New York Times reported.

The contractors, who were not injured, were working for the Army Corps of Engineers, repairing the main levee breach that flooded so much of the city.

"Our understanding was that they were driving across the bridge, and they took refuge behind or under cars," said Eugene Pawlik, a spokesman for the corps.

Broussard, the Jefferson Parish president, wondered where the troops were. He wept on camera yesterday as he described one man's desperate phone calls with his elderly mother, who was trapped in a nursing home in St. Bernard Parish day after day without help.

"And she drowned Friday night," Broussard said, sobbing. "She drowned Friday night."

Officials in Jefferson, in Plaquemines Parish to the southeast and St. Bernard to the east of New Orleans -- parts of which were under several feet of water after the storm -- have complained bitterly about communications breakdowns with state and federal authorities that left these areas without help for days.

Amos Cormier, chairman of the Plaquemines Parish Council, said he saw no sign of the Federal Emergency Management Agency, or the National Guard until Saturday. He said the National Guard had been requested Wednesday.

Troops were moving into the Mississippi coast, bringing water and ice, helping to keep order, said Stacey Morrison of the Mississippi Emergency Management Agency. She said the American Red Cross had set up more than 100 shelters in the state.

Conditions in some of the shelters were awful, one doctor said.

"There are a lot of feces everywhere: in the hallways, in the grass and all around," said Kim Kwiatek, a doctor with a FEMA medical assistance team from Ohio working at Biloxi Regional Medical Center.

At Biloxi Regional and Memorial Hospital at Gulfport doctors reported many cases of diarrhea, vomiting, skin rashes, and cuts from people moving debris. So far, doctors are not seeing the serious infectious diseases likely to breed when people are exposed to bad drinking water and fetid flood waters.

President Bush was scheduled to visit the Gulf Coast for the second time in four days today. Yesterday, he and first lady Laura Bush toured American Red Cross headquarters in Washington yesterday, thanking all for their work, asking the public for donations and showing confidence in the recovery effort.

Nonetheless, officials were put on the defensive again and again yesterday as reporters kept asking for some response to the criticisms.

CNN's Wolf Blitzer asked Chertoff: "Are you humiliated by what happened?"

Chertoff insisted that the scale of the calamity was so monstrous it overwhelmed any preparations that might have reasonably been made.

"It was unprecedented. ... Apocalyptic is the right description," Chertoff said. "We responded as rapidly as we could."

James Lee Witt, the Clinton administration FEMA director hired to advise Louisiana's governor, described the crisis yesterday in the state as "our worst nightmare."

Witt said yesterday that he thought the reorganization that put FEMA under the Department of Homeland Security had hurt the agency's ability to deal with natural disasters, and he said a lot of resources also had been depleted by the war in Iraq. But he declined to criticize federal, state or local officials in this disaster: "I think they worked as fast as they could to do whatever they could."

Rep. William J. Jefferson, a Democrat who represents the New Orleans area, was not so reticent. He criticized the government's push to get everyone out of the city in view of the danger of standing fetid water, downed power lines, no power and no clean running water.

Most of New Orleans' population of about 480,000 had by late yesterday either been moved to or were expected to be moved to shelters in 22 states as far north as Minnesota and west to California. Nearly half were in Texas alone.

This enormous population movement has touched off a kind of refugee crisis. Social service agencies, businesses, volunteer groups, military bases and other refugee shelters raced to help the multitudes find jobs, obtain their Social Security checks, receive their medicines, get their mail, locate missing relatives and pets, and enroll their youngsters in school.

Some had started looking for jobs, doing what they could to ease the nagging uncertainty.

Torres Smith, 42, a machine operator at a New Orleans seafood plant before Katrina hit, was evacuated along with his wife and four children, and is sleeping on a cot in the Astrodome.

"As far as I can tell, this is going to be our new home for a long time," he said. "I'll do anything -- cut grass, wash windows, wax floors. I can't just sit around here, looking at people lying in their cots."

The Associated Press and Sun staff writer Stephen Kiehl in Baton Rouge contributed to this article. Arthur Hirsch reported from Baltimore.

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