Four people from the same family died in their home from carbon monoxide poisoning in the town of Rugi, Tuscany, the Italian news agency ANSA reported, quoted by BTA.
The victims are a 48-year-old man, a 43-year-old woman and the couple's two children - a 22-year-old man and a 15-year-old girl, sources said.
A fifth person who was in the house is alive but is in critical condition in hospital, the sources said.
Three carabinieri officers who responded to the report suffered minor poisoning, the sources added.