Bank investors have been spoiled the past few quarters with outsize profit reports, so when several lenders post just OK earnings it's a reason to sell.

In recent trading Tuesday, the Philadelphia KBW Bank Index was down 2%, outpacing the decline in the broader market. Financial stocks also were knocked down by fears of rising interest rates, which were fueled by a stronger-than-expected March retail sales report.

Shares of Commerce Bank ( CBH) were hit particularly hard on the day, dropping $3.35, or 5%, to $63.20 after the New Jersey-based regional lender announced first-quarter earnings rose 44% from a year ago. The bank said it earned $62 million, or 75 cents a share, compared with $43 million, or 60 cents a share.

Commerce's numbers matched the Thomson First Call consensus estimate. But there were a few chinks in the report.

To start, the bank's total revenue of $316 million came in a bit lighter than some on Wall Street had expected. In a somewhat contentious conference call, Commerce Chairman Vernon Hill disputed the notion that the bank suffered a revenue miss and said expectations of a higher number were nothing more than a "rumor."

The bank also surprised some by reporting that the dollar value of its nonperforming loans -- loans overdue by at least 90 days -- rose by $10 million from a year ago to $33.1 million.

Commerce executives dismissed the increase as a mere hiccup due to "one or two commercial credits" going sour. But the rise in overdue loans comes at a time when most banks are seeing continued improvement on the credit front.

It wasn't just Commerce's earnings report that is spooking bank investors.

Last week, SunTrust ( STI), the large Southeast regional lender, kicked off the bank earnings season by saying it still hasn't seen any signs of a revival in borrowing by big corporate customers.

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