Police in Italy say they have arrested a nurse on suspicion of murdering 13 patients being treated in a state-run hospital in Tuscany.

Police said Thursday that the woman was arrested on Wednesday evening.

According to investigators, the deaths occurred from 2014-2015 while the patients were being treated in the anesthesia and reanimation department of the state-run hospital in Piombino, a coastal city about 70 kilometers (43 miles) southwest of Florence.

Authorities were planning a news conference on the investigation.

The arrest comes just weeks after a court in Ravenna convicted a nurse of killing a 78-year-old patient with a lethal injection. She was sentenced to life in prison.