WASHINGTON (Reuters) - The Federal Deposit Insurance Corporation, which insures bank deposits, said on Wednesday it is keeping a close eye on the unpaid real estate loans that are piling up at U.S. banks and thrifts.

"We remain vigilant," FDIC Chairman Sheila Bair said at a news conference on U.S. banks' second-quarter rise in noncurrent real estate loans. "We are closely monitoring the situation in the markets as well as individual institutions."

In a sign of distress that borrowers are facing, U.S. banks' non-current real estate loans rose for the fifth consecutive quarter to $66.9 billion at the end of the second quarter, the FDIC said. That was up 36 percent from one year ago and up 10.6 percent from the end of the first quarter, according to the FDIC.

Non-current loans are those for which payments are overdue by at least 90 days.