A doctor and two nurses have been charged with murdering hospital patients in the US city of New Orleans after Hurricane Katrina last year.
A lawyer for Dr Anna Pou said she was innocent of the charges
The three, who were arrested and then released on bail, are accused of giving lethal injections to four people.
At least 34 patients died at Memorial Medical Center, which was cut off after Katrina hit the city on 29 August.
Prosecutors have investigated claims of negligence and euthanasia, and subpoenaed 73 staff in the inquiry.
Dr Anna Pou and nurses Lori Budo and Cheri Landry have been charged with four counts of second-degree murder.
They are accused of giving four patients - two in their 90s and two in their 60s - lethal doses of morphine and a sedative.
Louisiana Attorney General Charles C Foti said: "This is not euthanasia. This is homicide."
He added: "While I am aware of the horrendous conditions that existed after Hurricane Katrina... I believe that there is no excuse for intentionally killing another living human being."
He said he expected more arrests to follow.
A lawyer for Dr Pou said she was innocent of the charges.
Patients at the 317-bed hospital spent four days stranded in floodwater, with no electricity, after Hurricane Katrina struck Louisiana.
Before rescuers reached the hospital, at least 34 patients had died.
Tenet Healthcare Corporation, which owns Memorial, said the arrest warrants alleged that the medics "may have administered pain medication that hastened the deaths of certain patients in the chaotic aftermath of Hurricane Katrina".
"If proven true, these allegations are very disturbing. Euthanasia is repugnant to everything we believe as ethical healthcare providers, and it violates every precept of ethical behaviour and the law."
In all, more than 970 people are known to have died in Louisiana in the aftermath of Katrina, and more than 200 in neighbouring Mississippi.
In a separate case, two nursing home owners were charged with manslaughter last year over the deaths of dozens of people at the St Rita's home.
They are accused of ignoring orders to move residents out.