Jin Lee/Associated Press

JPMorgan Chase disclosed on Friday that losses on its botched credit bet could climb to more than $7 billion and that the bank’s traders may have intentionally tried to obscure the full extent of the red ink on the disastrous trades.

Mounting concerns about valuing the trades led the company to announce that its earnings for the first quarter were no longer reliable and would be restated. Federal regulators, who were already examining the trades, are now looking at whether employees of the nation’s biggest bank by assets intended to defraud investors, according to people with knowledge of the matter.

The revelations left Jamie Dimon, the bank’s chief executive, scrambling for the second time within two months to contain the fallout from the trading debacle. It has already claimed one of his most trusted lieutenants, compelled Mr. Dimon to appear before Congress to account for the blunder and prompted the bank to claw back millions in compensation from three traders in London at the heart of the losses. A top bank official said that the board could also seize pay from Mr. Dimon, but did not indicate that it would do so.

Since announcing initial losses of $2 billion in May, Mr. Dimon, once vaunted for his risk prowess after navigating the bank deftly through the financial crisis, has worked to prove that any flaws in risk management are limited to the chief investment office, a once-obscure unit with offices in London and New York. But the latest news is prompting fresh questions about whether risk controls throughout the bank are weak.

“This points to fundamental and potentially widespread risk management failure,” said Mark Williams, a professor of finance at Boston University, who also served as a Federal Reserve Bank examiner.

Frank Franklin II/Associated Press

Much more than profits are at stake for Mr. Dimon. The mounting problems from the soured bets strengthen the hand of lawmakers in Washington who have been pushing to curtail the kind of risk-taking that led to the trading losses.

The possible deceptions came to light in a regulatory filing early Friday just before the bank reported its second-quarter earnings. While the bank posted a profit of nearly $5 billion despite the trading losses of $4.4 billion for the quarter, some analysts and regulators zeroed in on the valuation of the trades.

“If traders misrepresented a fact with the intent to defraud, they can be subject to criminal charges,” said Alan R. Bromberg, a securities law expert at Southern Methodist University.

In contrast, investors appeared to accept Mr. Dimon’s pledges that the bank had rooted out the problems and could reap record annual profits. They rallied behind the bank, sending its shares up nearly 6 percent, the best among its peers on an overall strong day for American stocks.

If the trades had been properly valued, the bank said it would have lost $1.4 billion on the position in the first quarter, bringing the total losses to $5.8 billion so far this year. In a conference call with analysts on Friday, Mr. Dimon said that the trade, under the worst market conditions, could result in another $1.7 billion in losses.

In a rare move, the bank seized millions in pay from three managers in the unit’s London office who had “direct responsibility” for the blunder. People with knowledge of the clawbacks said that pay was taken back from Achilles Macris, Javier Martin-Artajo and Bruno Iksil, the trader who gained infamy as the London Whale for his large credit trades.

A lawyer for Mr. Macris declined to comment. A lawyer for Mr. Martin-Artajo could not be reached. Raymond Silverstein, a lawyer for Mr. Iksil, said his client believed he had “done nothing wrong and that he will be exonerated in due course.” While the company did not indicate the total tally for the clawbacks, Douglas Braunstein, the bank’s chief financial officer, said the bank could claim roughly two years of total compensation, including stock options.

Ina R. Drew, the senior executive who resigned as head of the chief investment office shortly after the trading losses, volunteered to give back her pay. The giveback is a precipitous fall for Ms. Drew, once one of Mr. Dimon’s most trusted executives. Ms. Drew earned roughly $14 million last year, making her the bank’s fourth-highest-paid officer. Ms. Drew declined to comment.

JPMorgan said that an internal investigation, led by Mike Cavanagh, a former chief financial officer at the bank, unearthed questions about how traders in the bank’s chief investment office were valuing their bets. After combing through thousands of e-mails and phone call records of traders, senior executives at the bank feared that traders, in an attempt to disguise the magnitude of the losses, improperly marked their trades.

“Certain individuals may have been seeking to avoid showing the full amount of the losses in the portfolio during the first quarter,” the bank said in a statement, but didn’t indicate how many traders may be embroiled in the mismarking.

Certain tough-to-exit trades can be extremely difficult to value, according to current and former traders in the chief investment office. On some positions, “valuing a trade is like throwing a ball at a target while blindfolded,” said a former trader who requested anonymity because of the continuing investigations into the trade. The Securities and Exchange Commission, which is one of several federal regulators investigating the trading losses, is interested in the valuation of the trades, according to a person briefed on the investigation.

Separately, federal regulators from the Office of the Comptroller of the Currency and the Federal Reserve Bank of New York stationed at the bank’s Manhattan headquarters have been examining the valuation of the trades in weekly meetings with the staff at the chief investment office, according to current regulators who insisted on anonymity because the investigations have not concluded.

Mr. Cavanagh said that the executives within the unit were outmatched by the increasing complexity of the bets being made as the unit grew over the last several years. JPMorgan, Mr. Cavanagh, emphasized, is undertaking a “complete revamp of C.I.O. management.” Part of that change began Friday, when the bank announced that Irvin Goldman, who had overseen risk for the chief investment office, was resigning.

Started roughly five years ago, the unit, which grew from a sleepy operation into a profit center, was also torn by internal strife between deputies in New York and London, according to current and former traders.

Mr. Dimon emphasized that the investment office was going to focus on conservative investments. The bank has moved the majority of the soured trade to JPMorgan’s investment banking unit, where Mr. Cavanagh told analysts risk controls were strong.

Mr. Braunstein, the chief financial officer, told analysts that the decision to refile first-quarter earnings was made on Thursday, the day before the bank reported its second-quarter results. The change means that revenue for the first quarter fell by $660 million, and net income dropped by $459 million.

Mr. Dimon urged analysts Friday to focus on the bank’s overall strength.

The bank reported a $4.96 billion profit for the second quarter, down 9 percent from $5.43 billion a year earlier. Revenue also fell to $22.2 billion, down 17 percent from the same period last year.

“All of our client-driven businesses had solid performance,” Mr. Dimon said.

At one point during the earnings call, Mike Mayo, an analyst with Crédit Agricole Securities, asked whether the bank had reached a “tipping point” where it had become too unwieldy to manage.

Mr. Dimon answered with a succinct “no.”

JPMorgan, for its part, has emphasized that the trading loss is a blip in terms of the bank’s overall profitability. Mr. Dimon added that while the bank is “not proud of this moment, we are proud of this company.”