"This is a very difficult moment for me, both as a mayor and as a man," said mayor Filippo Nogarin in a Facebook post on Monday evening, in which he announced the investigation.
Nogarin explained that he had been questioned by regional public prosecutors on Tuesday, adding that he was "not surprised" by the news of the investigation.
As mayor of the city, Nogarin is in charge of the local Civil Protection Agency, and he said: "It's clear that faced with the deaths of eight people, the investigators have to look into every detail and examine the conduct of each of the actors involved" with relief efforts during the flood.
Nogarin pictured in 2016. Photo: Giuseppe Cacace/AFP
Livorno took the brunt of the flooding when storms lashed the country in mid-September last year.
Four of the victims were from the same family, including a grandfather who was able to rescue his three-year-old granddaughter but died when he went back to try to save her brother.
By the time the search effort was concluded, the death toll from the flooding had risen to eight.
Many more families were evacuated from their homes, some by boat and some children carried through flooded streets on firefighters' shoulders. The start of the autumn school term was also postponed in the worst-affected areas due to the extreme weather.
AS IT HAPPENED: Evacuations and school closures as storms lash Italy
At the time, Nogarin criticized the government for underestimating the potential danger beforehand, issuing a code orange alert for the region rather than red.
"We didn't expect this because the alert was orange. Then we woke up to this," he said, describing Livorno as “a city on its knees”.
The bad weather was aggravated by severe drought over the summer, which left land drier than usual and unable to soak up the rains.
An aerial photo shows the extent of the flood damage across Livorno. Photo: Italian Fire Service