A German nurse is suspected of killing at least seven seriously ill patients in less than one year, the prosecutor's office in the eastern Bavarian town of Straubing said on Wednesday. "We are not just looking into these seven cases," said the lead investigator in the case, Klaus-Dieter Fiedler. The 48-year-old woman, who worked at the Saint Elisabeth hospital in Straubing, was arrested on Tuesday. Hospital managers said it had been noticed that morphine had gone missing. The hospital is one of the biggest in the state of Bavaria, with more than 17,000 patients treated every year. Prosecutors in Bavaria are currently investigating a case in which a male nurse is suspected of killing 29 patients by poisoning them.