An Italian doctor and his nurse lover arrested this week near Milan are suspected of killing dozens of people from 2011-2014, including the woman's husband, prosecutors said on Thursday.
Emergency room anaesthetist Leonardo Cazzaniga, 60, and nurse Laura Taroni, 40, were held on Tuesday over the deaths of at least five patients elderly patients but prosecutors are now examining the medical files of more than 50.
The couple is also suspected of killing Cazzaniga's father, as well as Taroni's mother and Taroni's 45-year-old husband, who the couple reportedly tricked into believing he was diabetic.
Taroni's spouse died on June 30, 2013 after regularly taking medicine that was "absolutely incongruous with his actual health conditions, weakening and eventually killing him," according to a police report.
A cocktail of medicines, including extremely high doses of morphine and Propofol was administered to the murdered patients "in overdoses and in rapid succession" at Saronno Hospital, about 30 km north-west of Milan, where Cazzaniga and Taroni worked together, prosecutors said.
Wiretapped conversations allegedly in the possession of investigators recorded the couple talking about killing other relatives, as well as Taroni discussing the "perfect murder" with her 11-year-old son.
In one of the most disturbing calls, Taroni told Cazzaniga she was also prepared to kill her son and her eight-year-old daughter, wiretaps allegedly reveal.
"If you want, I'll kill the children," she told Cazzaniga, who replied: "No, not the children."
There is no evidence that Cazzaniga and Taroni were practising unauthorised euthanasia or that they were motivated by compassion.
"Every now again I have this urge to kill someone - I need to," Taroni allegedly told Cazzaniga in an intercepted conversation.
According to one of Cazzaniga's colleagues, the anaesthetist frequently referred to himself as an "angel of death".
Prosecutors are also probing 14 people, including the top management of Saronno hospital, for failing to investigate the suspicious deaths. Regional health authorities have pledged to set up a committee of enquiry over the issue.
One of the people under investigation, a female doctor, is allegedly suspected of blackmailing the hospital into hiring her in exchange for keeping quiet about the murders and of helping Taroni falsify blood tests results to convince her husband he had diabetes.
An Italian nurse, Fausta Bonino, was arrested in Tuscany in March on suspicion of killing 13 patients but was released from custody in April pending further investigations.
