The U.S. government charged Tuesday that Bank of America Corp. defrauded investors when it sold $850 million worth of mortgage-backed securities, a new hurdle in the bank's quest to persuade investors its legal troubles are in the past.

The Department of Justice and Securities and Exchange Commission filed parallel civil actions in federal court in North Carolina alleging that the second-largest U.S. bank by assets understated the risks associated with mortgage-backed securities in 2008.

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