Real estate lender Colonial BancGroup Inc. has been shut down by federal officials in the biggest U.S. bank failure this year.

The Federal Deposit Insurance Corp., which was appointed receiver of the Montgomery, Alabama-based Colonial and its about $25 billion in assets, said the failed bank’s 346 branches in Alabama, Florida, Georgia, Nevada and Texas will reopen as offices of Winston-Salem, North Carolina-based BB&T.

The FDIC has approved the sale of Colonial’s $20 billion in deposits and about $22 billion of its assets to BB&T Corp.

Four other banks closed

Regulators also closed four other banks: Community Bank of Arizona, based in Phoenix; Union Bank, based in Gilbert, Arizona; Community Bank of Nevada, based in Las Vegas; and Dwelling House Savings and Loan Association, located in Pittsburgh.

The closures boosted to 77 the number of federally insured banks that have failed in 2009. That compares with 25 bank failures last year and three in 2007.

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