Credit Suisse, the bankrupt Swiss bank bought by UBS Group in a hastily-drafted rescue plan earlier this month, could bring new legal and regulatory challenges to its new owner over helping wealthy Americans avoid paying taxes in the US, reports CNBC.

For years, the bank provided a haven for wealthy American clients to hide assets from the IRS, even after it was caught and indicted more than a decade ago, according to two former Credit Suisse bankers who told CNBC in exclusive interviews. and work with the US government as whistleblowers.

In 2014, the bank pleaded guilty to criminal charges for “knowingly and intentionally” helping thousands of US customers hide their offshore assets and income from the IRS.

Credit Suisse then admitted to using shell entities, destroying accounts and delivering cash to U.S. clients to avoid detection by the IRS, agreeing to prevent U.S. tax evasion as part of a plea deal.

Credit Suisse also agreed to a number of reforms, including disclosing cross-border activities and cooperating with authorities when they request information, among other things.

The bank appears to have violated that agreement, according to a new report by the US Senate Finance Committee that details abuses since then.

The report, released Wednesday, details the findings of the commission’s two-year investigation, and is all the more important given the looming banking crisis.

Earlier this month, the Swiss National Bank, the country’s central bank, poured more than $100 billion in cash into Credit Suisse to keep it afloat, and the Swiss government agreed to give UBS about $9 billion to protect it from takeover losses.

US Senate investigators say the new revelations raise questions about how much American money remains hidden in the vaults of a bank whose collapse rocked the foundations of the global banking system.

The Senate report, prepared by Democratic members of the committee, accused the bank of violating the terms of a 2014 plea agreement, which could have a range of consequences if the Justice Department pursues the case.

It’s unclear how much potential liability UBS faces as a result of the report, but a lawyer for the whistleblowers says the bank should pay up to $1.3 billion.

Senate Finance Committee Chairman Ron Wyden, R-Oregon, said his committee received new information just this week from Credit Suisse about other undisclosed U.S. accounts the bank had after 2014.

“This is ongoing, only in the last two days more money has been discovered that was hidden, and there are very significant problems here. Clearly, it’s time to prosecute and make sure there are penalties that send a strong message,” Wyden said.

“Credit Suisse employees facilitated and facilitated a large illegal tax evasion scheme,” said an adviser to the finance committee, who spoke on condition of anonymity because the report has not yet been released.

“To date, no Credit Suisse employee involved in the scheme has faced any consequences from the United States government for their involvement,” he added.

Senate investigators say they found that Credit Suisse allowed 25 American families to hide more than $700 million in bank capital in the years following Credit Suisse’s plea deal.

Two former Credit Suisse employees who worked as whistleblowers with the U.S. government and Senate investigators told CNBC that some of the wrongdoing continued long after Credit Suisse’s 2014 plea deal.