A crisis in the markets inevitably leads to a push for greater regulation. And ever since Enron, it leads to criminal investigations.

The Federal Bureau of Investigation has begun preliminary inquiries into whether fraud contributed to the turmoil at Lehman Brothers, American International Group, and Fannie Mae and Freddie Mac, the Wall Street Journal, the New York Times, and Associated Press report.

The Times cites a government official who tells the paper that it was "logical to assume" that the four would come under scrutiny, given the manner in which they collapsed or had to be rescued.

Indeed, there is growing political pressure to find culprits. Taxpayer are not happy that their bill for cleaning up the credit-crisis mess will be heading to more than $1.8 trillion if Congress passes some version of the proposed $700 billion bailout plan.

A joint mortgage task force was formed by the F.B.I., the Internal Revenue Service, and the Justice Department earlier this year. At the time, federal officials indicated that the task force would have a broad mandate to investigate how mortgages were bundled into securities and how those securities were sold and disclosed.

Federal prosecutors in Brooklyn have already set the bar for future cases, winning an indictment against two former Bear Stearns hedge fund managers, accusing them of securities and wire fraud charges stemming from the collapse of two hedge funds that had invested heavily in pools of securities backed by subprime-mortgage debt. At the time, federal prosecutors indicated that they would look at other investment firms.

The Bear case has raised concerns that prosecutors will be looking to criminalize incompetence. And there will be plenty of examples of that to be found.

Many people took home millions, even as the pillars of the financial system were beginning to shake after the subprime-mortgage market imploded. Political leaders, if not the American people, want some heads.

Yet there may not be a central figure whose prosecution can satiate the populist anger; someone like Charles Keating, a banker who came to represent the scandals in the S&L crisis, as the Wall Street Journal notes.

At a Senate Judiciary Committee hearing last week, Robert Mueller, the director of the F.B.I., said that the agency has 1,400 investigations into mortgage brokers, appraisers, buyers, and lenders.

"But we also have 24 investigations looking at the larger corporations, who may have engaged in misstatements in the course of what transpired during this financial crisis," Mueller said.

Senator Patrick Leahy, a Vermont Democrat and member of the committee responded, "If people were cooking the books, manipulating, doing things they were not supposed to do, then I want people held responsible."