Authorities are investigating some "relatively large corporations" as part of a sweeping mortgage-fraud probe.

Some 19 companies, including mortgage lenders, investment banks, hedge funds, credit-rating companies and accounting firms, are being looked at, officials said.

The Justice Department and FBI officials sought to demonstrate progress in the mortgage fraud fight announcing that roughly 400 individuals have been criminally charged for their roles in home-lending schemes, with 670 recent arrests. Real-estate developers, brokers, agents and appraisers were among those charged, along with lenders, lawyers and so-called straw buyers.

"Operation Malicious Mortgage" has swept up criminal investigations from March 1 through mid-June, and produced 144 cases nationwide. FBI officials estimate the losses from the alleged scams reached $1 billion.