A nurse is suspected of inadvertently tainting intravenous painkillers at St. Cloud Hospital while seeking drugs, spreading bacterial infections to 23 patients since October, the hospital said on Wednesday.

The nurse has been suspended and St. Cloud Hospital has launched an investigation with state health officials into the infections possibly caused when drugs were diverted from IV bags for personal use, said the hospital, in the city of the same name 70 miles northwest of Minneapolis.

A criminal investigation is under way and the hospital and state health department are trying to determine if other patients were infected, it said. The 23 known infected patients had hospital stays in one unit from October to early March.

"We take this matter very seriously," St. Cloud Hospital President Craig Broman said in a statement. "Our highest priority is to provide safe, quality patient care."

St. Cloud Hospital said it launched the investigation in February after staff members noticed "increased incidence of organisms that do not normally infect people."

The hospital has not identified the nurse or the drugs alleged to have been diverted from patients. It described the investigation as preliminary.

There was no evidence that blood-borne pathogens such as Hepatitis B, Hepatitis C or HIV were transmitted to the patients who suffered from bacterial infections, it said.

The hospital tested all patient-controlled IV bags containing painkillers for bacteria as well as multiple supplies and environmental resources in its investigation, it said. The hospital said it also evaluated employees and hospital practices for distributing narcotics.