All 101 belonged to the 'Ndrangheta in Calabria, and included wealthy gangsters with close ties to bosses or with key roles within the organised crime group, a statement said.
Alessandro Pannunzi, the son of a man dubbed Italy's version of Colombian drug lord Pablo Escobar, was among those cashing in.
His father Roberto was “unanimously considered by Italian and American investigators to be one of the world's most important cocaine brokers, and who boasted that he did not count his money, but weighed it”, police said.
Alessandro's wife is the daughter of “one of the main Colombian cocaine producers,” it added.
Each mobster will have to pay back their share of the 516,000 euros ($566,000) stolen from the state, police said.
The wealthy mobsters had submitted claims for income support under false identities, Italian media reports said, and police were investigating whether those tasked with inspecting them may have had ties to the criminal underworld.
The poverty relief scheme known as the reddito di cittadinza, or “citizens' income”, is intended for the five million Italians living below the poverty line.
The 'Ndrangheta, which takes its name from the ancient Greek word for “courage”, is generally believed to have outgrown its Sicilian and Neapolitan competitors thanks to cocaine trafficking from Latin America.
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Its stronghold is Calabria in Italy's south, but it has become increasingly powerful in northern Italy and abroad too. Mafia experts say it is the only organised crime group present on every continent.
The income support sting came as warnings abounded in Italy over risks the mafia could flourish during the deep economic recession caused by its economically devastating national lockdown.
Experts warn usury is already on the rise and crime groups will also be looking to feast on public aid meant for suffering businesses.