The more intricate schemes — appraisal fraud, fraudulent flipping of property, use of straw buyers and identity theft — often are committed with the complicity of real estate industry insiders like agents, mortgage brokers, appraisers and title examiners. Some fraud does not become evident until mortgage loans become delinquent.

Last year, the FBI and other law enforcement agencies mounted "Operation Quick Flip," an effort to disrupt and dismantle mortgage fraud rings. From July 5 through Oct. 27, a total of 81 people were arrested, 156 individuals and companies were indicted, 89 convictions were obtained and 60 people received prison sentences, according to the government. Lenders suffered $606.8 million in losses from the actions of those involved, the government said.

The FinCen report cited a number of types of false statements used in mortgage fraud, including altered bank statements, altered or fake documentation of earnings such as W2 forms and income tax returns, fraudulent letters of credit, misrepresentation of employment, altered consumer credit scores, invalid Social Security numbers, failure to fully disclose a borrower's debts.

In addition, some mortgage brokers have used identities of prior customers to obtain loans for new customers who cannot qualify.

The regulators also found schemes in which borrowers signed multiple mortgages on the same property from multiple lenders and fraudulent bankruptcy filings to stall or prevent foreclosure.