The Louisiana attorney general's office launched the probe after a doctor at New Orleans' Memorial Medical Center told CNN that some of the 45 patients who died there might have been euthanized to end their suffering when the storm hit on Aug. 29. A total of 1,035 people were killed in Louisiana by Katrina's winds and flooding.
Orleans Parish Coroner Frank Minyard said his staff had examined all but six of the bodies from Memorial and that nothing obviously suspicious had been found.
State spokeswoman Kris Wartelle told USA Today that investigators were also reviewing New Orleans' Lindy Boggs Medical Center, where 19 people died after the storm.
The probe also includes St. Rita's nursing home in St. Bernard Parish, where 34 people died in the rising waters after Katrina hit. The operators have been charged with 34 counts of negligent homicide for not evacuating residents.