US regional banking stocks fell sharply on Thursday after two banks disclosed issues with bad and fraudulent loans, amplifying concerns on Wall Street around the state of credit markets.

Zions Bancorp announced it had a $50m charge-off over two bad loans from its subsidiary, California Bank & Trust in San Diego. Western Alliance also said it was dealing with a fraudulent borrower.

Zions stock was down over 11% by Thursday afternoon, while Western Alliance was down over 10%. Shares of Jefferies Financial Group were down 9% for the day.

The sell-off knocked the wider market, with the benchmark S&P 500 down 0.7% and the Dow Jones down 0.6% in New York.