Two former JPMorgan Chase & Co. (JPM) employees were charged by U.S. prosecutors with attempting to conceal trading losses at the largest U.S. bank last year as part of a probe of its $6.2 billion loss on derivatives bets.

Javier Martin-Artajo, a former executive who oversaw the trading strategy at the bank's chief investment office in London, and Julien Grout, a trader who worked for him, were charged with conspiracy to falsify books and records and conspiracy to commit wire fraud and false filings in a complaint unsealed today in Manhattan federal court. The two men engaged in a scheme to falsify securities filings between March 2012 and May 2012, according to the complaint.

JPMorgan Chief Executive Officer Jamie Dimon characterized the $6.2 billion loss as "the stupidest and most-embarrassing situation I have ever been a part of." First disclosed in May 2012, the bad bets led to an earnings restatement, a U.S. Senate subcommittee hearing and probes by the Securities and Exchange Commission and U.K. Financial Conduct Authority.

Dimon, 57, whose own pay was cut in half, pushed out senior executives including former Chief Investment Officer Ina Drew, who oversaw the London unit where the loss took place. The bank said it clawed back more than $100 million in pay from employees who were involved with, or oversaw, the trade.

`London Whale'

Bruno Iksil, the Frenchman at the center of the case who became known as the "London whale" because his portfolio was so large, has been aiding the FBI and federal prosecutors for months in their probe as part of an agreement with the government for leniency, three people with direct knowledge of the situation said.

Attorneys for Martin-Artajo and Grout didn't immediately respond to a request for comment on the charges. An attorney for Iksil declined to comment.

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