WASHINGTON — The FBI is investigating failed bank IndyMac Bancorp Inc. for possible fraud, an official said Wednesday of the government's latest target following the collapse of the nation's subprime mortgage market.

It was not immediately clear how long the FBI's probe of the bank has been ongoing — or whether it was opened before last Friday's takeover of IndyMac by the Federal Deposit Insurance Corp.

The investigation appears to be focused on the company and not individuals who ran it, a law enforcement official told The Associated Press. The official spoke on condition of anonymity because he was not authorized to speak publicly about the investigation.

IndyMac Bank's assets were seized by federal regulators after the mortgage lender succumbed to the pressures of tighter credit, tumbling home prices and rising foreclosures. The bank is the largest regulated thrift to fail in the last 20 years, regulators said.

IndyMac's operations were transferred to the FDIC because bank regulators did not think the lender could meet its depositors' demands. The FDIC is now running the bank under the name IndyMac Federal Bank, FSB.