The firefighters were responding to an explosion in the Alessandria province in the northwestern Piedmont region around midnight, Italian daily La Repubblica reported. As firefighters worked to put out the fire, a second blast went off and leveled the building.
Two firefighters were confirmed dead, while a third was initially declared missing, Italy’s fire and rescue service said. Two more firefighters and a police officer suffered injuries.
After hours of searching, firefighters found the body of their fellow member buried underneath rubble from the collapsed building, the service said.
Prosecutor Enrico Cierci told La Repubblica that a timer and gas canister were recovered from the rubble, which makes them "think the explosion was deliberate.” The timer was operated remotely, Italy’s Sky TG24 reported.
Authorities reportedly questioned the owner of the farm building, which had been renovated and has been up for sale for two years.
While investigators haven’t found a motive for the blast, Alessandria police superintendent Michele Morelli told Sky TG24 there was no indication of terrorist involvement.
Italy's interior minister, Luciana Lamorgese, visited the site, amid an outpouring of sympathy for the families of the victims from Italian officials and authorities.
Lamorgese declined to comment on the investigation.
The Associated Press contributed to this report.