The department's criminal division is building cases against several financial institutions and their employees, including traders at Barclays, the British bank, according to government officials close to the case who spoke on the condition of anonymity because the investigation is continuing. The authorities expect to file charges against at least one bank later this year, one of the officials said.
The prospect of criminal cases is expected to rattle the banking world and provide a new impetus for financial institutions to settle with the authorities. The Justice Department investigation comes on top of private investor lawsuits and a sweeping regulatory inquiry led by the Commodity Futures Trading Commission. Collectively, the civil and criminal actions could cost the banking industry tens of billions of dollars.
Authorities around the globe are examining whether financial firms manipulated interest rates before and after the financial crisis to improve their profits and deflect scrutiny about their health. Investigators in Washington and London sent a warning shot to the industry last month, striking a $450 million settlement with Barclays in a rate-rigging case. The deal does not shield Barclays employees from criminal prosecution.
The multiyear investigation has ensnared more than 10 big banks in the United States and abroad. With the prospects of criminal action, several firms, including at least two European institutions, are scrambling to arrange deals, according to lawyers close to the case. In part, they are trying to avoid the public outcry that stemmed from the Barclays case, which prompted the resignation of top executives.
The criminal and civil investigations have focused on how banks set the London interbank offered rate, known as Libor. The benchmark, a measure of how much banks charge one another for loans, is used to determine the borrowing costs for trillions of dollars of financial products, including mortgages, credit cards and student loans. Cities, states and municipal agencies also are examining whether they suffered losses from the rate manipulation, and some have filed suits.
With civil actions, regulators can impose fines and force banks to overhaul their internal controls. But the Justice Department would wield an even more potent threat by bringing criminal fraud cases against traders and other employees. If found guilty, they could face jail time.
The criminal investigations come at a time when the public is still simmering over the dearth of prosecutions of prominent executives involved in the mortgage crisis. The continued trouble in the financial sector, including the multibillion-dollar trading losses at JPMorgan Chase, have only further fueled the anger of consumers and investors.
But the Libor case presents a potential opportunity for prosecutors. Given the scope of the problems and the number of institutions involved, the rate-rigging investigation could provide a signature moment to hold big banks accountable for their activities during the financial crisis.
"It's hard to imagine a bigger case than Libor," said one of the government officials involved in the case.
The Justice Department has jurisdiction over the London bank rate because the benchmark affects markets in the United States. It could not be learned which institutions the criminal division is chasing next.
According to people briefed on the matter, the Swiss bank UBS is among the next targets for regulatory action. The Commodity Futures Trading Commission is pursuing a potential civil case against the bank. Regulators at the agency have not yet decided to file an action against the bank, nor have settlement talks begun. UBS has already reached an immunity deal with one division of the Justice Department, which could protect the bank from criminal prosecution if certain conditions are met. The bank declined to comment.
The investigation into the global banks is unusually complex and it could continue for years, and ultimately end in settlements rather than indictments, said the officials close to the case. For now, regulators are building investigations piecemeal because the facts of the cases vary widely. That could make it difficult to compile a global settlement, although some banks would prefer an industrywide deal to avoid the harsh glare of the spotlight, said a lawyer involved in the case.
American authorities face another complication as they build cases. Investigators still lack access to certain documents from big banks.
Before gathering some e-mail and bank records from overseas firms, the Justice Department and American regulators need approval from British authorities, according to the people close to the case. But officials in London have been slow to act, the people said. At times, British authorities have hesitated to investigate.
By contrast, the Justice Department and the Commodity Futures Trading Commission have spent two years building cases together. Lanny Breuer, head of the Justice department's criminal division, has close ties with David Meister, the former federal prosecutor who runs the commission's enforcement team.
In the Barclays case, the British bank was accused of reporting false rates to squeeze out extra trading profits and fend off concerns about its health. During the crisis, banks feared that reporting high rates would suggest a weak financial position.
Lawmakers in London and Washington are examining whether regulators looked the other way as banks artificially depressed the rates. On Friday, it was disclosed that a Barclays employee notified the Federal Reserve Bank of New York in April 2008 that the firm was underestimating its borrowing costs. Despite the warning signs, the illegal actions continued for another year.
But in April 2008, a senior enforcement official at the Commodity Futures Trading Commission, Vincent McGonagle, opened an investigation. He directed the case along with another longtime official, Gretchen Lowe.
At first the case stalled as the agency waited months to receive millions of pages of documents when Barclays pushed back against the American regulators, according to the officials close to the case. By the fall of 2009, the trading commission received a trove of information, providing a broad view into the wrongdoing.
A series of incriminating e-mail and instant messages, regulators say, laid bare the multiyear scheme. In one document, a Barclays employee said the bank was "being dishonest by definition."
The case gained further traction in early 2010, when the agency's enforcement team engaged the Justice Department. The department's criminal division, led by Mr. Breuer, agreed that regulators had a strong case. The investigation continued until January 2012, when the trading commission notified Barclays lawyers that they were entering the final stages before deciding about an enforcement action.
As part of the deal, regulators pushed the bank to adopt new controls to prevent a repeat of the problems. Among other measures, the bank must now "implement firewalls" to prevent traders from improperly talking with employees who report rates.
The bank says that it provided extensive cooperation during the three inquiries, and has spent around $155 million on its own three-year investigation. Because it agreed to settle with British authorities, Barclays received a 30 percent fine reduction.
In the United States, Barclays offered to pay a fine of $200 million to the C.F.T.C., slightly below the initially proposed range, according to government officials close to the case. Mr. Meister's team soon accepted the offer, securing the biggest fine in the commission's history.
On June 27, British and American authorities announced the deal with Barclays, which agreed to pay more than $450 million total. "For this illegal conduct, Barclays is paying a significant price," Mr. Breuer said then.
Susanne Craig contributed reporting.