Wall Street has been worried about bad loans for weeks. Now those fears are spreading

Investors are on high alert for financial groups that potentially lent to companies that engaged in fraud. Michael Nagle/Bloomberg/Getty Images

Several financial groups are wrestling with bad loans, raising worries on Wall Street of more to come.

For weeks, investors have focused on Jefferies Financial Group, an investment bank that has at least $45 million worth of exposure to First Brands, an auto-parts supplier that filed for bankruptcy last month.

But on Thursday, they turned some of their attention to two regional banks, Western Alliance Bancorp and Zions Bancorp, after concerns about some of their loans as well.

All three banks’ stocks suffered their steepest single-day losses in over six months on Thursday. That anxiety played out in the market at large as well, with the Dow