The Wall Street Journal reported that regulators in the U.S. and UK are probing up to a dozen banks, including Citigroup, to investigate whether senior executives knew of, or participated in, illegal activity in connection with alleged efforts to manipulate LIBOR.

The Journal noted that shortly after Tokyo-based trader Tom Hayes was fired by Citigroup for trying to manipulate benchmark rates, he sent a letter to one of the bank’s human resources executives saying that his actions were consistent with others at Citigroup Japan.

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Previously on monitordaily.com Brokers Charged in LIBOR Investigation, published July 17, 2013