(Bloomberg) -- Bank of America is being investigated by the SEC over whether the lender broke rules designed to safeguard customer accounts, according to the Wall Street Journal.

The bank’s Merrill Lynch unit used a variety of large, complex trades and loans over a three-year period to save on funding costs and free up billions of dollars in cash and securities for trading that the firm would otherwise have needed to keep off-limits, the newspaper reported Tuesday, citing people familiar with the inquiry without naming them.

Bank of America stopped the trades in mid-2012, and now the SEC is investigating whether the strategy violated customer- protection rules and if the company misled regulators about its actions, the paper said.

The strategies were in place when Bank of America bought Merrill Lynch in 2009 and the company “fully complied with the rules designed to safeguard client funds,” Bill Halldin, a spokesman for the Charlotte, North Carolina lender, said in an e-mailed statement.

John Nester, a SEC spokesman, declined to comment on the report.

--With assistance from Hugh Son in New York and Dave Michaels in Washington.

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