Wall Street's industry-funded regulator is examining ties between Credit Suisse Group AG and a number of trading firms over concerns that the Swiss bank enabled potentially improper trading, The Wall Street Journal reported, citing people familiar with the probe.

The Financial Industry Regulatory Authority (FINRA), in the past few weeks, has sent inquiries to the bank on hundreds of suspect trades by clients of the firm, the paper reported late on Wednesday.

FINRA is investigating whether the clients' trading operations, many of which are overseas, violated U.S. anti-money-laundering rules, the Journal reported.

Credit Suisse plans to cut its ties with several of the firms, according to people familiar with the probe and the firms, the paper reported.

Credit Suisse was not immediately available for comment.

The probe comes as Credit Suisse became the largest bank in decades to plead guilty to a U.S. criminal charge earlier this week and said it would pay more than $2.5 billion in penalties for helping Americans evade taxes.