JPMorgan Chase said Friday that its traders may have tried to conceal the losses from a soured bet that has embarrassed the bank and cost it almost $6 billion - far more than its CEO first suggested. The bank said an internal investigation had uncovered evidence that led executives to question the integrity" of the values, or marks, that traders assigned to their trades. JPMorgan also said that it planned to revoke two years' worth of pay from some of the senior managers involved in the bad bet, and that it had closed the division of the bank responsible for the mistake. "This has shaken our company to the core," CEO Jamie Dimon said. The bank said the loss, which Dimon estimated at $2 billion when he disclosed it in May, had grown to $5.8 billion. The investigation, which covered more than a million emails and tens of thousands of voice messages, suggested traders were trying to make losses look smaller, the bank said. The revelation could expose JPMorgan to civil fraud charges. If regulators decide that employee deceptions caused JPMorgan to report inaccurate financial details, they could pursue charges against the employees, the bank or both. JPMorgan could not necessarily hide behind the actions of its employees. Regulators could decide that its oversight or risk management contributed to the problematic statements.