The U.S. Department of Justice has expanded its money-laundering probe to Citigroup Inc's Mexican unit, Bloomberg reported on Friday.
Citigroup's Banamex USA unit was already under investigation by U.S. regulators for possible breaches of anti-money laundering laws.
The bank on Wednesday said it would shut its Banamex USA operations and pay US$140 million to resolve allegations that the unit violated federal laws requiring banks to maintain adequate anti-money laundering programs.
The latest investigation looks at whether Citigroup let customers move illegal cash through Banco Nacional de Mexico, Bloomberg said, citing documents it had reviewed.
The Mexican unit was subpoenaed by the DOJ in January for information about its anti-money-laundering controls, seeking documents about its due diligence on operations involving hundreds of clients, the report said.
Mexico City-based Banco Nacional de Mexico embarrassed Citigroup last year when it lost more than US$500 million on fraudulent loans to a supplier to state-run oil giant Pemex .