Louisiana Attorney General Charles Foti Jr. is "looking into" the response at six hospitals and 13 nursing homes to Hurricane Katrina and the subsequent flooding, a spokeswoman said.
The review includes a search warrant executed Saturday at Memorial Medical Center, New Orleans.
Memorial's owner, Tenet Healthcare Corp., said investigators collected medical records and other documents. During Katrina's aftermath, 34 patients died on the campus, including 10 at Memorial and 24 at a long-term acute-care hospital operated within Memorial by LifeCare Holdings, Tenet said.
Foti spokeswoman Kris Wartelle described the investigation as "more criminal than civil" and said both Memorial and LifeCare were under scrutiny. She declined to say if warrants had been served on other facilities.
Tenet said representatives of the attorney general's office told the company that investigators planned to search other hospitals and nursing homes.
Foti already charged two owners of a nursing home with 34 counts of negligent homicide for failing to evacuate residents in a timely fashion.