The deaths took place while terminally ill patients were being driven to their family homes from hospital in the Sicilian town of Biancavilla.
The scheme had reportedly been going on since 2012, and the 'Ambulance of death' operation, as it was named by investigators, has looked at over 50 deaths in the area to establish whether any could have been homicides.
Of these, 12 were considered "particularly meaningful" to the operation, the Catania deputy prosecutor told a press conference, but only three were presented to the investigating magistrate as evidence.
The magistrate issued an arrest order for the 42-year-old driver, who is suspected of voluntary homicide aggravated by the alleged mafia involvement.
Catania's public prosecutor opened the investigation after an informant gave them details about the scheme and alleged local mafia groups' involvement. He had previously spoken about the case on Italian TV show Le Iene.
According to Italy's Rai News, the informant said that the driver injected air into the patients' blood using a needle, and that they died of embolism. He then allegedly took advantage of the family's grief to recommend a funeral company which paid him €300 for each job it got through his recommendation.
READ ALSO: Five ways to fight the mafia