WASHINGTON — Now-defunct IndyMac Bancorp Inc. is under investigation by the FBI for possible fraud in connection with home loans made to risky borrowers, The Associated Press has learned.

It was not immediately clear how long the FBI's probe of the bank has been ongoing.

The investigation is focused on the company — which was taken over last Friday by the FDIC — and not individuals who ran it, according to a law enforcement official who 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 and the second largest financial institution to close in U.S. history, regulators said.

The Office of Thrift Supervision said it transferred IndyMac's operations to the Federal Deposit Insurance Corporation because it did not think the lender could meet its depositors' demands.

FDIC spokesman David Barr could not immediately be reached for comment Wednesday.

Over the last year, and faced with a cratering housing market, the FBI has opened a wide-ranging probe of companies across the financial services industry, from mortgage lenders to investment banks that bundle home loans into securities sold to investors.

Countrywide Financial Corp., the nation's largest mortgage lender, is also under scrutiny.

Additionally, two former Bears Stearns managers were indicted last month on conspiracy and securities and wire fraud charges alleging they lied to investors in a hedge fund that tanked last year as the subprime market collapsed. Those charges marked the first criminal charges to arise on Wall Street from the subprime mortgage debacle.