The owners of a nursing home outside New Orleans have been charged with manslaughter over the deaths of 34 people during Hurricane Katrina.
The Manganos face 34 charges of negligent homicide
The married couple who ran St Rita's home are accused of ignoring mandatory orders to evacuate residents, whose bodies were found last week.
These are believed to be the first criminal neglect charges laid in connection with the flood disaster.
The death toll in Louisiana is now 423 after the discovery of more bodies.
On Sunday, 45 bodies were found at a flooded hospital in New Orleans. The owners said they had been critically ill patients who died in stifling heat after power was cut off, and insisted they could not have been evacuated in time.
The overall confirmed death toll in the hurricane-affected states is above 600.
News of the nursing home charges came as President George W Bush took some blame for the slow response to the disaster on 29 August.
"To the extent that the federal government didn't fully do its job right, I take responsibility," he told reporters at the White House.
The BBC's Jonathan Beale in Washington says Mr Bush's admission does not mean he is prepared to take all the blame but has again pointed to failures throughout government.
In other developments:
- Vulnerable islands are evacuated and mainland schools closed in North Carolina as tropical storm Ophelia reaches hurricane strength off the coast
- Three New Orleans suburbs - Gretna, Westwego and Lafitte - are poised to reopen having restored basic amenities
- Louisiana's prison service confirms no inmates died or escaped during the storm and warns all those missing on bail or probation to re-establish contact.
Mable Mangano and Salvador Mangano Sr were charged with negligent homicide after they surrendered to police in Louisiana and have been taken into custody.
The elderly residents died in the rising flood waters after the couple allegedly discounted the evacuation orders and repeated warnings as the hurricane approached.
"Thirty-four people drowned in a nursing home when it should have been evacuated - I cannot say it any plainer than that," said Louisiana Attorney General Charles Foti.
The owners allegedly 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, Mr Foti added.
A lawyer for the couple, Jim Cobb, told CNN his clients had not abandoned any of the patients and were not told of any mandatory evacuation order.
"If you evacuate these patients, many of whom are on oxygen, many of whom are on feeder tubes, many of whom won't survive the evacuation, many of those people are going to die," Mr Cobb said.
Counting the dead after the storm is proving to be controversial in other ways, the BBC's Daniel Lak reports from New Orleans.
A single day increase of more than 180 deaths in the official toll is being blamed on reports from rural areas arriving late in the state capital, Baton Rouge.
Louisiana Governor Kathleen Blanco also accused the federal government of refusing to pay for the collection of dead bodies - an allegation it denies.
"No one, it seems, even those at the highest level, seems to be able to break through the bureaucracy," Ms Blanco said at a meeting of Louisiana officials.
"I'm angry and outraged by this situation."
Political and bureaucratic disputes were said to have delayed rescue efforts soon after the hurricane struck, our correspondent notes, and it appears they are continuing.