Dozens of mafia bosses could be released from prisons across Italy due to the risk of Covid-19 infection, after Italian judges set free at least three ageing mobsters, placing them under house arrest.

News magazine L’Espresso on Wednesday reported that a judge in Milan had ordered the release of one of the most influential bosses of Cosa Nostra, Francesco Bonura, 78, who was serving a 23-year sentence. The terms of Bonura’s release to house arrest allow his movement for health-related appointments.

In recent weeks judges also ordered the release from prison of Vincenzino Iannazzo, 65, and Rocco Santo Filippone, 72, both alleged ’Ndrangheta bosses. Judges feared that a Covid-19 infection could be lethal for Filippone since he suffers from serious cardio-vascular disease.

“It is a very alarming situation,” said Leo Beneduci, secretary general of Osapp, Italy’s largest prison police officers’ union. “In Italy there are approximately 12,000 members of criminal organisations in prison. Members of the penitentiary police have begun reporting detainees who embrace each other with the alleged goal of increasing the possibility of contracting the virus and getting released from prison.”

The department of penitentiary police circulated an internal memo, seen by the Guardian, asking prison officials for the names of prisoners suffering from specific illnesses and who are over the age of 70 because they are “at risk of complications in case of Covid-19 infection”.

There are currently 74 bosses over 70 and with serious health conditions held under article 41-bis of the Italian penal code, which allows the authorities to suspend usual prison entitlements with the aim of severing ties with criminal associates on the outside. The prisoners include Leoluca Bagarella, 78, a Sicilian boss responsible for dozens of homicides, Raffaele Cutolo, 78, the leader of the Nuova Camorra Organizzata, currently serving multiple life sentences for murder, the bloodstained bosses of the Bellocco clan of the ’Ndrangheta and the Sicilian “boss of bosses” Nitto Santapaola, 81.

The president of Sicily’s antimafia commission, Claudio Fava, said he feared mafia bosses could leverage the coronavirus crisis to secure their release. “As infections have begun to wane, [potentially] releasing bosses in isolation under 41-bis, like Santapaola and Bagarella, is hypocritical and an offence toward the thousands of elderly victims of this virus,” said Fava, whose father, Giuseppe, was killed by the mafia on Santapaola’s orders.

The justice minister, Alfonso Bonafede, clarified on Wednesday that the decision to release Mafiosi was not taken by the government and that he would look into the reports.

“The risk is that we’ll find the mafia virus on the streets alongside Covid-19,” said Lirio Abbate, journalist and national editor of L’Espresso, who currently lives under police protection after receiving numerous death threats from the mafia. “It would be a double pandemic that we mustn’t allow to happen.”