As part of the government’s efforts to tackle the subprime loan crisis federal prosecutors have charged over 400 people in the U.S. with mortgage fraud.

The effort, known as Operation Malicious Mortgage, was created to send the message that housing crime is a national program according to FBI Director Robert Mueller and Deputy Attorney General Mark Filip. Filip said, “The Department of Justice is determined to detect and to punish mortgage fraud and to help restore the stability and confidence in our housing and credit markets,” in a recent press conference in Washington.

Nicolas Retsinas, director of the Joint Center for Housing Studies at Harvard University said the increase in subprime lending has created a “fertile environment for all kinds of things, including outright fraud.” Retsinas believes this criminal activity is one more reason for investors and lenders to be concerned about the valuations of investments and loans.

Authorities estimate that more than $1 billion has been lost due to the mortgage frauds. The different schemes include cheating lenders, swindling those facing foreclosure and filing fraudulent bankruptcy claims according to officials. There are real estate agents, lawyers, appraisers and borrowers among the indicted.

This operation focused mainly on individual cases and small crime rings, but officials have reported that they are also looking into 19 companies, including investment banks and hedge funds that are believed to have participated in accounting fraud among other white-collar crimes dealing with mortgage securities.