The FBI and the US Department of Justice are examining whether there was any criminal wrongdoing in losses that have damaged the reputation that JP Morgan and Mr Dimon have built for risk management.
America's largest bank by assets has been battling to contain the fallout from the losses, which Mr Dimon described as "self-inflicted".
Yesterday, at the bank's annual shareholder meeting in Tampa, Florida, the banker admitted: "It should never have happened. I can't justify it."
The 56 year-old, one of the most powerful bankers on Wall Street, said he would consider clawing back the bonuses of any executives found to be responsible.
The losses have already cost Ina Drew, the head of the bank's chief investment office, her job and more are expected to leave the bank.
Mr Dimon yesterday refused to say how long its own internal investigation will take, but said the bank would "do the right thing".
In a further blow to Mr Dimon, whom President Barack Obama once described as his "favourite banker", 40pc of JP Morgan's shareholders voted to split his dual role as chairman and chief executive.
The crisis is the biggest that Mr Dimon has faced since shepherding JP Morgan through the financial crisis. Just a month ago, he dismissed reports about large trades the bank was making in an obscure corner of the derivatives market as nothing more than a "tempest in a teapot". Yesterday, he promised shareholders that "we will do the right thing" in investigating the losses.
But there was little sign of the controversy abating yesterday. John Liu, who runs New York City's pension fund, yesterday joined the call for bonuses of those executives responsible for the losses to be taken back.
The disclosure of the losses in the credit derivatives market has reignited the debate in the US over whether more regulation is needed to ensure the safety and soundness of the financial system.
Mr Dimon has been one of the most outspoken critics of the wave of regulation since the financial crisis, but insisted to shareholders that he was in favour of "sound and strong" regulation.
JP Morgan, which employs thousands of people in the City of London, has warned that the $2bn losses could deepen over the course of the year.
While some shareholders at the Florida AGM offered support to Mr Dimon, others were alarmed and baffled at the scale of the losses that the bank said it ran up in six weeks. "I'd like to have a clearer sense of the risk that I'm taking when I invest in JP Morgan," said Eric Vlahov, a shareholder. "Right now you don't."
Although the proposal to appoint an independent chairman failed to win the support of the majority of shareholders, the size of the vote in favour may have surprised the bank's board.
Most votes are likely to have been submitted before the trading losses were disclosed last Thursday. However, 91.5pc of shareholders backed the pay of Mr Dimon, which totalled $23m last year.
