SAO PAULO (Reuters) - Brazil’s federal police on Thursday launched a raid targeting Itaú Unibanco Holding SA as part of a probe into alleged bribery of tax officials, a source briefed on the matter said.

In a statement, the police confirmed 34 search warrants are being served in the states of São Paulo, Rio de Janeiro and Pernambuco. The new phase of the so-called “Operation Zealot” investigates a banking institution which the federal police did not name.

The probe relates to alleged “collusion” between a member of the CARF, a Finance Ministry body that hears appeals on tax disputes, and the unnamed banking institution, the statement said.

The source, who confirmed the target is Itaú, said the raids mark a new phase of Operation Zealot, which investigates the alleged involvement of banks and companies in the bribing of Brazilian tax auditors to waive or reduce tax payments.

The wrongdoing was allegedly related to business conducted by the local unit of FleetBoston Corp that Itaú bought a decade ago, according to the source. It involved law firms and consultancy firms and allegedly took place between 2006 and 2015, the police statement added.

Spokespeople at Itaú were not immediately available for comment.