BBC's PatrickO'Connell: More investigations are underway

The criticism is contained in a report by the General Accounting Office, the investigative arm of the US Congress, on the movement of funds in the early 1990s belonging to Raul Salinas, brother of the former Mexican President, Carlos Salinas De Gotari.

The officials accuse Citibank of using various means to disguise the source of up to $100m such as waiving bank references for Mr Salinas, assisting his wife to use another name and other separate allegations, which, it says, broke the paper trail of the funds.

Broke rules but not the law

The report concludes that the bank facilitated a money managing system that disguised the origin, destination and beneficial owner of the funds involved.

But while the report says Citibank broke its own rules, it stops short of alleging the bank broke the law. The US Department of Justice is conducting a separate criminal inquiry into the affair.

'Errors' in the report

A Citibank spokesman told the BBC that the report contains errors of fact and interpretation. It says it is committed to combating money laundering and that it co-operates fully with law enforcement authorities.

Raul Salinas is currently in a Mexican prison on murder and corruption charges.

In October, the Swiss authorities accused him of depositing more than $100m of drugs money into Swiss banks, obtained through helping Mexican and Colombian drug cartels.