NEW YORK (AP) —

Wall Street is concerned about the health of the nation’s regional banks, after a few of them wrote off bad loans to commercial customers in the last two weeks and caused investors to wonder if there might be more bad news to come.

Zions Bank, Western Alliance Bank and the investment bank Jefferies surprised investors by disclosing various bad investments on their books, sending their stocks falling sharply this week. JPMorgan Chase CEO Jamie Dimon added to the unease when he warned there might be more problems to come for banks with potentially bad loans.

“When you see one cockroach, there are probably more,” Dimon told investors and reporters on Tuesday, when JPMorgan reported its results.

The KBW Bank Index, a basket of banks tracked by investors, is down 7% this mon

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