Bloomberg reported that Bruno Iksil, the former JPMorgan trader whose bets caused more than $6.2 billion in losses last year, is now central to any U.S. charges against his former colleagues.

Bloomberg said that prosecutors may announce charges as early as this week against former London-based JPMorgan employees, accusing them of trying to mask losses on a complex derivatives portfolio.

Bloomberg noted, citing three people with direct knowledge of the matter, that Iksil, the Frenchman who became known as the London Whale because of his trading book’s size, has been cooperating with the FBI and the Manhattan U.S. Attorney’s office for months in their probe of the bank’s biggest trading debacle ever.

To read the Bloomberg story click here.