The 57-year-old nun was jailed on suspicion of links to a mafia group whose influence extends throughout Italy and Europe.
Anna Donnelly had built an unshakable reputation and was respected in Milan, but suddenly it became known that the woman may have been working with a group called the 'Ndrangheta.
The nun was arrested. It is believed that she acted as an intermediary between the gang and the imprisoned criminals, Reuters reports.

Police suspect the woman led a double life. She is known for her work in poor areas of Milan. She was recently awarded the public prize "Golden Panettone".
At the same time, Donnelly visited prisons in Milan, Pavia, and Rome on charitable missions.
Under this cover, since 2010 she has become a reliable intermediary between the mafia and prisoners, law enforcement officials believe.
It is noted that the woman did not receive monetary compensation for her work. It is a question of "exchange of services."
The investigation is in full swing. In addition to the nun, 25 people have been arrested, including two politicians. It is also reported that funds in the amount of 1.8 million euros (197.6 million rubles) have been seized.