U.S. investigators are reviewing whether some banks colluded to manipulate an interest rate before and during the financial crisis, The Wall Street Journal reports. The regulators, headed by the U.S. Department of Justice and the Securities and Exchange Commission, are probing whether U.S. and European banks understated their own borrowing costs, which are used to calculate the London interbank offered rate (Libor). They are investigating whether the banks effectively formed a global group and coordinated on how to report borrowing costs between 2006 and 2008. The probe is focusing on banks, including Bank of America, Citigroup and UBS, which have been sent subpoenas.

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