WASHINGTON — The US Justice Department Thursday charged three former Credit Suisse bankers and a Swiss trust company founder with helping wealthy Americans evade US taxes by keeping money in secret Swiss bank accounts.

The indictment did not mention Credit Suisse by name, since it was the individual bankers, not the bank itself, who were indicted.

But Credit Suisse announced last week that it was the target of a US Justice Department investigation, which is typically a prelude to an indictment, and media reports indicate that Credit Suisse is the bank in question.

Those charged are Markus Walder, the former head of Credit Suisse's North America Offshore Banking, Susanne D. Ruegg Meier, a former manager at the bank, Andreas Bachmann, a former banker at a Credit Suisse subsidiary, and Josef Dorig, the founder of a Swiss trust company.

According to the indictment, the four bankers "engaged in illegal cross-border banking that was designed to assist US customers evade their income taxes by opening and maintaining secret bank accounts at the bank and other Swiss banks."

The US Justice Department, which announced the charges, said that as of late 2008, the bank maintained thousands of secret accounts for US customers with as much as $3 billion in total assets under management.

In its statement last week, Credit Suisse said the probe "concerns historical private banking services provided on a cross-border basis to US persons."

Thursday's Justice Department statement noted that the conspiracy to help US citizens evade taxes dated back to 1953, and involved "two generations of US tax evaders including US customers who inherited secret accounts at the international bank."

Four other Credit Suisse bankers -- Marco Parenti Adami, Emanuel Agustino, Michele Bergantino and Roger Schaerer -- were charged in a similar indictment in February.

The indictments against the former Credit Suisse bankers come after another damaging case against rival Swiss bank UBS.

Not only was UBS made to pay a $780 million fine, but the Swiss government was also forced to ease the country's banking secrecy rules to allow the bank to hand over 4,000 case files on US clients suspected of tax evasion.

According to the indictment against the former Credit Suisse bankers, the bank's employees destroyed statements and other account records sent by email or fax to its office in New York "so that records regarding the undeclared accounts would not be maintained in the United States."

They also advised their US customers to make their withdrawals in amounts less than $10,000 in order to try to hide the secret bank accounts and transactions from US authorities.

If convicted, each defendant could face up to five years in prison and a maximum fine of $250,000.