Some Wall Street giants were saved by the Federal Reserve and others are awaiting the $700 billion government bailout, but before that can happen, the Federal Bureau of Investigation (FBI) might have something to say about it, CNN reported.

The FBI has launched an investigation into potential mortgage fraud at Fannie Mae, Freddie Mac, Lehman Bros. Holding Inc. and American International Group Inc., and officials believe the executives of these companies might be involved.

“The FBI currently has 26 pending corporate fraud investigations involving subprime lenders,” Special Agent Richard Kolko, a spokesman for the bureau, told CNN. “As we have seen, this number can fluctuate over time. However, we do not discuss which companies may or may not be the subject of an investigation.”

CNN reported that the sources could not speak on the record about the companies involved, because the investigation is ongoing. However, earlier this month FBI Director Robert Mueller told Congress that 1,400 individual real estate lenders, brokers and appraisers, as well as nearly 25 corporations, were under investigation.

Sources told CNN that the investigations into the four financial service giants are still in the early stages and that the probe was the next step in discovering what happened at these companies that caused them to be in such financial turmoil.

The FBI sought assistance from the Internal Revenue Service in order to launch its investigation into mortgage fraud, and in June its Mortgage Fraud Task Force arrested more than 400 mortgage brokers, lenders and appraisers and other industry insiders, who the task force claimed were responsible for more than $1 billion in losses.

It was also reported earlier that Bank of America Corp.’s newly acquired Countrywide Financial Corp. might also be under FBI investigation as well.