This is the second biggest bank failure in US history, so it seems only obvious that the Feds will be involved and trying to find out if the mistakes made were honest ones or something more sinister.

IndyMac was taken over by regulators last week, and now we learn it's being investigated for possible fraud. Sources with knowledge of the investigation tell CNN the FBI is looking into whether any crimes were committed when IndyMac made home loans to risky borrowers. The FBI would not comment, but one source says the investigation is focused on the company and not individuals at this time.

I would suspect that they are looking at bad appraisals, bad underwriting which would mean false statements on loan applications.

And now that the bank has been taken over by regulators, experts say it will be easier for the Feds to get their hands on what they need to conduct their probe.

There's been so many issues associated with the mortgage failures and the subsequent losses that the question is whether the FBI has enough resources working these cases.

The Bureau says it's made investigating mortgage fraud a priority and assigned nearly 200 agents. In all, it's investigating 21 companies, officials won't offer any details, but CNN has previously confirmed that the nation's largest mortgage lender - Countrywide Financial is part of that probe.

Our mortgage fraud caseload has doubled in the past 3 years to more than 1,400 pending investigations. We have engaged each of our 56 field officers to focus on this criminal priority.

And these investigations are very complicated. They take a lot of time, so don't expect any announcements anytime soon.

For CNNMoney.com, I’m Kelli Arena.