MINNEAPOLIS -- A Kimball nurse has pleaded guilty to stealing pain killing drugs while working at St. Cloud Hospital.

42-year-old Blake Zenner admitted he accessed lock boxes while working as a registered nurse and used syringes to remove the drug Dilaudid from intravenous bags. In some cases he injected saline into the bags to replace the missing drug.

The crimes took place from November 2010 to March 2011.

Authorities say as a result of Zenner's actions, 25 hospital patients were infected with bacteria.

Zenner faces up to four years in a federal prison. His sentencing date has not yet been set.