Kenneth Kaiser, FBI assistant director for the Criminal Investigative Division, said the FBI has developed an initiative focused on subprime mortgage loan fraud and is working with investigators from other federal agencies.

CNN: FBI investigating 14 companies for mortgage fraud

Like many American lenders exposed to the U.S. mortgage market, WaMu was hurting for cash as a result of the subprime loan crisis.

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One cause was the continuing deterioration of loan performance as mortgage rates have risen: almost one in five subprime mortgages are now delinquent by more than 30 days or in foreclosure.

ECONOMIST: The subprime meltdown, continued

Others allegedly were steered into costly subprime loans, even though they could have qualified for a prime mortgage, the type of loan offered to borrowers with the best credit histories.

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