WASHINGTON (AP) -- Regulators have closed a small bank in Arizona, bringing the number of U.S. bank failures to 13 this year.

The Federal Deposit Insurance Corp. on Tuesday seized Central Arizona Bank, based in Scottsdale, Ariz.

The lender, which operated a single branch, had roughly $31.6 million in assets and $30.8 million in deposits as of March 31.

Western State Bank, based in Devils Lake, N.D., agreed to assume all of the failed bank's deposits and to buy essentially all of its assets.

The failure of Central Arizona Bank is expected to cost the deposit insurance fund $8.6 million.

The lender is the second FDIC-insured institution in Arizona to fail this year.

U.S. bank closures have been declining since they peaked in 2010 in the wake of the financial crisis and the Great Recession.

In 2007 just three banks went under. That number jumped to 25 in 2008, after the financial meltdown, and ballooned to 140 in 2009.

In 2010 regulators seized 157 banks, the most in any year since the savings and loan crisis two decades ago. The FDIC has said 2010 likely was the high-water mark for bank failures from the recession. They declined to a total of 92 in 2011.

Last year bank failures slowed to 51, but that's still more than normal.

In a strong economy an average of only four or five banks close each year. The sharply reduced pace of closings shows sustained improvement.

From 2008 through 2011, bank failures cost the deposit insurance fund an estimated $88 billion, and the fund fell into the red in 2009. With failures slowing, the fund's balance turned positive in the second quarter of 2011.

By Dec. 31 it stood at $32.9 billion, up from $25.2 billion at the end of September.

The FDIC expects bank failures from 2012 through 2016 to cost $10 billion.