Numerous Italian newspapers reported on Monday how prosecutors were focusing on 25 individuals in connection with the dairy group's spectacular collapse last December.
Though no sources were quoted, the Corriere della Sera newspaper speculated that founder and former chairman Calisto Tanzi was also likely to be arrested in the near future.
Parmalat, with 36,000 employees in 30 countries, was declared insolvent after reports of a gaping shortfall in its accounts.
Auditors have subsequently put group debt at €14.3 billion, equivalent to $17.8 billion.
Milan prosecutors are this week expected to list the names of about 20 bankers or bank employees in an official record of the investigation.
Italian police searched the Bank
of America offices in Milan
The move is a required step before charges are formally brought against an individual.
The probe is also being conducted by magistrates in the northern Italian city of Parma, close to Parmalat headquarters.
Italian and foreign banks have already been targeted by the investigation, notably for their links to former Parmalat management, as well as to savers and investors who had bought shares in the company.
Searches have been carried out at the Italian offices of the Bank of America and Deutsche Bank, as well as at a subsidiary of the leading Italian bank - Banca Intessa.