Since 2009, Swiss banks have been under the microscope of U.S. regulators.

That was the year UBS paid a $780 million fine for helping thousands of people evade taxes. And today, banks are still being investigated over the same allegations, reports Financial Times.

Read: U.S. probe into Swiss accounts reads like spy thriller

FT adds that due to ongoing cases, several banks in Switzerland have threatened to freeze the accounts of U.S. clients unless they offer proof they’re being tax compliant. Read more on legal experts’ views of the situation.

For more on taxes, read:

STEP 2014: Update on U.S. tax exposure

Two big banks to face criminal charges

Come clean with CRA