NEW YORK (CNNMoney.com) — Seven banks were shut down by authorities Thursday, pushing the tally of failed banks for 2009 to 52, more than doubling the failures in 2008.

The rash of Illinois failures are interlinked: All six banks were controlled by one family and followed a similar business model that “created concentrated exposure in each institution,” according to the FDIC.

The agency said that the six failures stemmed from the banks’ investments in collateralized debt obligations and other loan losses.