Citigroup (NYSE:C) was forced to write off $50 million after two traders allegedly attempted to manipulate interbank lending rates. The information has surfaced as part of an investigation being led by nine separate enforcement agencies in the United States, Europe, and Japan.

The agencies have been looking into whether U.S. and European banks manipulated the London Interbank Offered Rate, or Libor, the benchmark rate for $350 trillion worth of financial products, or any other interbank lending rates.

Two traders at Citigroup Tokyo allegedly attempted to manipulate the rate-setting procedure for the Tokyo Interbank Offered Rate, or Tibor. Citi reported the matter to regulators, unwound the traders’ positions, and wrote off the resulting loss of $50 million.

Barclays (NYSE:BCS) similarly reported a suspected manipulation of the Euribor by one of its employees, Philippe Moryoussef, who left the bank in 2007 and is currently employed with Nomura Singapore.

Addressing the allegations, a Nomura spokesman said: “Nomura is aware of the investigation into the setting of Euribor and Libor rates. The allegations against Mr Moryoussef are related to a period of time before he joined Nomura. We would point out the fact that Nomura is not a member of either the Euribor panel or the Libor panel, and therefore has no role in the setting of these rates.”

Banks such as Royal Bank of Scotland (NYSE:RBS), Deutsche Bank (NYSE:DB), UBS (NYSE:UBS), and JPMorgan (NYSE:JPM) have fired, suspended, or placed on administrative leave more than a dozen traders suspected of manipulating rates.

To contact the reporter on this story: Damien Hoffman at staff.writers@wallstcheatsheet.com

To contact the editor responsible for this story: Damien Hoffman at editors@wallstcheatsheet.com

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