Three Louisiana towns allowed people to come home yesterday for the first time since Hurricane Katrina struck, as officials from a nursing home and a hospital defended their handling of sick and aged patients who died after the storm.

As the Gulf Coast struggled to recover from the August 29 hurricane, the death toll rose to 648 in Louisiana, Mississippi and Florida. Louisiana Attorney General Charles Foti filed criminal charges against the operators of a nursing home where 34 patients died after they were trapped by the storm's floodwaters.

The cities of Gretna, Westwego and Lafitte, all suburbs of New Orleans, told residents they could come back at daybreak.

"Essential services such as electricity, sewerage and water are improving daily but are still not up to standard. Commercial establishments, such as grocery stores, gas stations and pharmacies are scarce but are beginning to open. Therefore, if you have the means to stay away for a longer period of time it would be advisable for you to do so," said a notice on the website of Jefferson Parish, where the towns are located.

Aaron Broussard, president of Jefferson Parish, said the key to reopening areas for habitation and business was restoring sewage services.

Fewer than 400,000 electricity customers still lacked power 16 days after Hurricane Katrina pummelled the US Gulf Coast in Louisiana and Mississippi, according to area utilities and the US Department of Energy.

About 319,000 of the homes and businesses in Louisiana, or 29 per cent, remained without power, while Mississippi had about 84,000 customers still with no service.

Mr Foti said on Tuesday that the owners of a nursing home in St Bernard Parish had been arrested and charged with 34 counts of negligent homicide.

"Thirty-four people drowned in a nursing home when it should have been evacuated. I cannot say it any plainer than that," Mr Foti said.

The owners, Mable and Salvador Mangano, turned down an offer from local officials to take the patients out by bus, and did not bother to call in an ambulance service with which they had a contract, he said. They were each released on $50,000 bonds yesterday.

Mr Foti vowed to investigate every death at every hospital and nursing home that was not from natural causes.

James Cobb, a lawyer for the owners, said they did all they could and had told family members that they could remove the patients if they wanted.

"What people have to understand is, you're presented with a horrible choice," he said. "You take people who are on feeder tubes, who are on oxygen, who are on medications and you put them on a bus to go 112 kilometres in 12 hours? People are going to die, people are going to die, we know that."

In another development, the owners of a New Orleans hospital where 44 bodies were found said they were those of critically ill patients who died in stifling heat after power was cut to the flooded building but before it could be evacuated.

Tenet Healthcare Corporation said no one still alive was left behind at Memorial Medical Center in New Orleans when help finally came.

"During more than four days with poor sanitation, without power, air-conditioning and running water, and with temperatures in the building approaching 43 degrees Celcius, some patients simply did not survive despite the heroic efforts of our physicians and nurses. We believe that most were very sick adult patients," the company said in a statement.

President George W. Bush, addressing the United Nations General Assembly, thanked other countries for coming to the aid of hurricane victims.

"In Alabama and Mississippi and Louisiana, whole neighborhoods have been lifted from their foundations and sent crashing into the streets. A great American city is working to turn the floodwaters and reclaim its future.

"To every nation, every province and every community across the world that is standing with the American people in this hour of need, I offer the thanks of my nation," he said.