The FBI says that deceptive practices at hedge funds and some banks may have made the subprime disaster worse. According to Reuters, the head of the agency said the bureau's investigation of potential fraud in the U.S. home mortgage industry now encompasses 19 companies in "cases that may have a substantial impact on the marketplace."

While insider trading and accounting fraud may be part of any charges which emerge, one of the biggest single issues may be the sales practices of the firms which sold subprime paper to their clients. The subprime instruments were often presented as having high credit ratings and safe risk profiles. Of course, it didn't work out that way. Another problem may be whether mortgage banks were completely honest in what they told home-buyers about how their loans would work as their interest rates increased over time.

Some of the investigation is a witch hunt. Large banks which took subprime instruments onto their balance sheets had plenty of genius-level analysts who could have examined the products. At most firms, so one skipped that part. Caveat emptor and all that. Individuals who took on home mortgages sold by people who did not want them to read the small print is another matter.

Rumors are that Goldman Sachs (NYSE:GS) and and Morgan Stanley (NYSE:MS) could be targets of the probe. Countrywide (NYSE:CFC) is already under investigation. One news report on the potential scandal said that FBI head man Robert Mueller told a meeting of lawyers "that their corporate clients should come forward and admit any wrongdoing before the FBI or Justice Department become involved.."

That'll be the day.

Douglas A. McIntyre is an editor at 247wallst.com.