Highmark Inc. will undertake a "complete investigation" of expenditures by the state's largest health insurer after last week's ousting of CEO Kenneth Melani, the board chairman told the Tribune-Review on Tuesday. "We'll be looking at anything that could be a problem," said Chairman J. Robert Baum, appointed acting CEO upon Melani's removal. "We're moving to make sure there wasn't any abuse." The audit is a standard procedure not linked to Melani's termination on Sunday, Baum said. Highmark's board fired Melani because Oakmont police said he struck his mistress's husband in a dispute that erupted when Melani went to the married couple's home on March 25 and would not leave.