Credit Suisse AG (CSGN.S) and UBS group AG (UBSG.S) are under scrutiny in a U.S. Department of Justice (DOJ) probe into whether financial professionals helped Russian oligarchs evade sanctions, Bloomberg News reported.

“The DOJ also sent subpoenas to employees of some major U.S. banks, the Bloomberg report said, adding the Swiss banks were included in a wave of subpoenas sent before Credit Suisse’s takeover by UBS.

The DOJ inquiries are to identify which bank employees dealt with sanctioned clients and how those clients were vetted over past years, Bloomberg reported.

The bankers may then be further investigated to determine if they broke any laws, the report added.

Credit Suisse and UBS declined to comment while the Justice Department did not immediately respond to Reuters’ emailed requests for comment.

The DOJ has been trying to pressure Russian oligarchs through sanctions, asset seizures and criminal probes to stop backing Russian President Vladimir Putin after the country’s invasion of Ukraine.

The Justice Department charged Russian oligarch Oleg Deripaska last year with violating sanctions by using the U.S. financial system to maintain three luxury properties”, - reads the article.