Government officials have stepped up an investigation into whether crimes were committed when the subprime-mortgage market collapsed.

The Federal Bureau of Investigation, the Internal Revenue Service, and federal prosecutors have formed a task force, report Lynnley Browning of the New York Times and Amir Efrati of the Wall Street Journal.

This new effort is apparently broader in scope than a task force formed by the F.B.I. in January that is looking at possible fraud in mortgage lending.

The Times says, "While the new task force is focusing on the role of mortgage lenders and brokers in low- or no-documentation loans, it is also examining how the loans were bundled into securities."

The investigation has accelerated in recent weeks, the Times says, as a growing number of banks reported additional write-downs on their securities tied to mortgages.

The Wall Street Journal quotes a federal prosecutor in Brooklyn, Benton Campbell, who says the "jury is still out" on whether crimes will be uncovered in the securitization of mortgages, their trading, or their disclosure.

"There are market forces in play in that area, and that doesn't necessarily mean there is fraud," Campbell told the Journal.

The United States attorney's office in Brooklyn, the Journal notes, is already investigating the collapse of two Bear Stearns hedge funds last summer and questions over how UBS valued its mortgage-backed-securities portfolio.