A heavily indebted man seeking to make a false insurance claim has confessed to setting off explosions which killed three firefighters at his house in north-west Italy, prosecutors have said.

Giovanni Vincenti told investigators he meant to blow up his farmhouse in the Piedmont region by setting off gas canisters, but he allegedly made a mistake with a timer and triggered two explosions, according to prosecutor Enrico Cieri.

Firefighters went to the property in Quargnento, near Alessandria, after the initial explosion early on Tuesday and were then struck by a second, stronger blast.

Vincenti was detained on Friday night. At a news conference on Saturday morning, Mr Cieri said Vincenti told investigators he had no intention of killing the firefighters.

The prosecutor said Vincenti could have prevented the deaths by telling firefighters tackling the first fire that there were more gas canisters in the house.

Mr Cieri said investigators found a manual for the timer in Vincenti’s bedroom. Vincenti’s wife is also under investigation.

Sky TG24 reported that the farm building had been renovated and had been up for sale for two years.

Funerals were held for the firefighters on Friday, attended by Italian premier Giuseppe Conte and other dignitaries.

Three other first responders were injured. One of the dead firefighters was buried under rubble, with the body only recovered after hours of digging.