WASHINGTON—A total of 775 banks, or one-tenth of all U.S. banks, were on the Federal Deposit Insurance Corp.'s list of "problem" institutions in the first quarter, as bad loans in the commercial real-estate market weighed on bank balance sheets.

Poor loan performance in other sectors also continued to hurt banks, with the total number of loans at least three months past due climbing for the 16th consecutive quarter, FDIC officials said in a briefing on Thursday.

"The banking system still has many problems to work through, and we cannot ignore the possibility of more financial market volatility," FDIC Chairman Sheila Bair said.

There were 702 on the FDIC's "problem" bank list at the end of 2009 and 252 at the end of 2008.