The U.S. military has begun door-to-door searches for survivors and the dead in the hurricane-ravaged areas of New Orleans and Mississippi.

It's a long, difficult process which officials say could take weeks, if not months.

Hundreds of thousands of survivors have evacuated to Texas, Tennessee and other states. But New Orleans Deputy Police Chief Warren Riley said Monday that many of the city's survivors still remained in the city, one week after Hurricane Katrina wreaked havoc on the Gulf Coast flooding New Orleans.

"There are, to our surprise, thousands of people that are in this city that we are trying to identify and locate," said Riley at a news conference.

"Unfortunately, there are some people who at this point do not want to leave the city. We are working with them, and talking to them and trying to convince them that there is absolutely nothing here for them to stay.

"We advise people that this city has been destroyed. It has been completely destroyed," Riley said.

Air Force Maj. Gen. Marvin S. Mayes said Air Force units have evacuated more than 3,000 patients out of New Orleans International Airport. He added that crews also have shuttled more than 15,000 people out of the swamped region.

But now, rescuers will now have to find the people who have "hunkered down," he said.

Reporting from New Orleans, CTV's Jed Kahane said there seems to be as many reasons as there are people for why some have chosen to stay behind in the ruined city.

Some refuse to leave their belongings for others to loot, while others don't want to leave their pets behind. And then there are those who refuse to believe everything has been washed away.

"We saw one man down in the old French Quarter with his bar open, saying, I'm staying put and going to be here to rebuild," said Kahane.

"It's incredible, as you drive around in what is a very quiet part of dry New Orleans. You see people amidst mountains of debris just sweeping up their little patch of sidewalk, trying to make it clean because it's something that they really need to do to survive, emotionally, in all this ruin."

Parish suburb residents return

Meanwhile, residents of an affluent New Orleans suburb were temporarily allowed to return to their homes Monday morning to collect some of their belongings.

A kilometres-long stream of cars inched into Jefferson Parish, west of the city, beginning at about 6 a.m. CT. About 460,000 residents are being allowed to collect what they need until Wednesday, when they will be required to leave once again.

Parts of Jefferson parish -- which lie on the other side of the 17th Street Canal where a levee breach flooded the downtown area -- escaped the worst of the flooding.

Tens of thousands missing

Body recovery teams, meanwhile, have begun the grim task of recovering the dead as rescues continue across the city.

About 60 bodies have been recovered so far, including 10 from the Louisiana Superdome where more than 20,000 people gathered in the immediate aftermath of Katrina.

But officials believe the death toll could easily be in the thousands.

New Orleans Mayor Ray Nagin told CTV's Lisa LaFlamme on Monday about 40,000 to 45,000 people remained unaccounted for.

"There was 500,000 people in this city before the storm. We evacuated probably 80 per cent of them which leaves about a hundred to a hundred and seven thousand.

"We have evacuated from the Superdome and the convention centre about 50,000 to 55,000 people. So that leaves you about 40 to 45,000 people unaccounted for."

Nagin said that while he's hoping that these people got out, authorities had to brace for the worst and expect that a percentage of these people had died.

As he spoke to LaFlamme, his continued frustration with the emergency response to date was evident.

"This problem is about process. This problem is about laws created many, many years ago that are not up to date to deal with this kind of crisis," Nagin said. "We can never let this happen again."

LaFlamme told CTV Newsnet that some rescue workers have been in the city for 48 hours and still haven't been assigned.

"One of the problems here is communication. There is really almost no cell service, so communicating with each other has been a challenge," LaFlamme said.

"There are hundreds of doctors who are parked about an hour from here, saying: 'Where do you want us? We've got medicine, we want to do these things to help out.'"

Despite the ongoing tension in the city, some progress has been made.

The U.S. Army Corps of Engineers said Monday that it has closed the 17th Street Canal breach, and is close to closing the London Street Canal breach.

Some smaller pumping stations had power restored and started working, but authorities estimate it might not be until late November before New Orleans is dry.

On Sunday, officials reported that only half of New Orleans is under water, whereas last Tuesday it was said that a shocking 80 per cent was flooded.

But as the floodwaters in New Orleans begin to recede, emergency workers are finding more and more of the dead.

The recovered bodies are being taken to refrigerated trucks at collection sites and then moved to a portable morgue near Baton Rouge.

Officials there will use DNA technology, dental records, fingerprints and photographs to identify the victims.

Elsewhere in the stricken Gulf Coast, Mississippi emergency officials said the state's death toll had reached 161. That number is also expected to rise.

Meanwhile, U.S. President George Bush visited Baton Rouge, La. and Poplarville, Miss. on Monday for his second trip to the region since the storm hit.

Speaking to emergency officials at Pearl River Community College in Poplarville, Bush pledged that "we're here for the long term."

"I understand. I understand the damage. I understand the devastation, I understand the destruction, I understand how long it's going to take. And we're with you. That's what I want you to know," Bush said.