Financial Crisis Inquiry Commission, a U.S. panel investigating the causes of the financial crises, may bring in outside accountants to scrutinize Goldman Sach's systems for data on its derivatives business, the panel's chairman told the Financial Times.

The commission will not back down from demands for information Goldman's executives have maintained they do not track, Chairman Phil Angelides told the newspaper.

"We have a deep level of questioning about whether we are getting the straight scoop here and whether Goldman is working with us on information that they surely have," Angelides told the paper.

Goldman's executives had earlier told the panel that the bank's accounting systems did not break out trading revenue generated strictly from derivatives.

"It defies logic that these institutions have no clue of how much money they are making or losing from these derivatives," Angelides told the paper.

Goldman could not immediately be reached for comment by Reuters outside regular U.S. business hours.