The country’s finance police are executing search warrants as they carry out asset seizures to the reported value of 12m euros (£9.1m).
The case involves 58 people involved in professional football, a Naples prosecutor said in a statement.
Lawyers for AC Milan said vice president Adriano Galliani was among those under investigation.
In a statement on the club’s website, the lawyers dismissed the allegations as unfounded and said they expected the case to be dismissed.
The investigation, dubbed ‘Fuorigioco’ (Offside), is believed to concern allegations of falsifying player transactions.