New York Attorney General Andrew Cuomo subpoenaed five Bank of America directors Wednesday as investigators prepare to file charges against the bank’s senior executives in connection with its acquisition of Merrill Lynch, according to a source familiar with the investigation.

Investigators believe the five directors have the most knowledge relevant to the inquiry, which focuses on whether Bank of America shareholders were misled about Merrill’s financial condition and executive bonuses before voting last December to approve the deal.

Cuomo’s probe is one of several investigations into Bank of America’s acquisition of the troubled investment bank.