In his remarks, Corzine apologized to MF Global's customers, investors and former employees who have suffered because of the bankruptcy. "Their plight weighs on my mind every day -- every hour," he said.

Corzine told lawmakers that he would attempt to answer questions and avoid relying on his Fifth Amendment right to remain silent. "As a former United States Senator who recognizes the importance of congressional oversight, and recognizing my position as former chief executive officer in these terrible circumstances, I believe it is appropriate that I attempt to respond to your inquiries," Corzine said. At the same time, "without adequate time and materials to prepare, I may be unable to respond to various questions," he said.

Corzine said he offered to testify to Congress without subpoena in January, by which time he might have been better able to prepare.

'Chaotic Days'

"I want to emphasize that, since my resignation from MF Global on November 3, 2011, I have not had access to the information that I would need to understand what happened," Corzine said. "It is extremely difficult for me to reconstruct the events that occurred during the chaotic days and the last hours leading up to the bankruptcy filing."

CFTC commissioner Jill Sommers, testifying in advance of Corzine, said regulators are still working to trace all the transactions and that some client funds may be recovered.

"If there is any customer money that has been transferred out of the accounts, that is part of what we are working together to find and that money will be clawed back to be distributed back to customers," Sommers, the commissioner overseeing the agency's investigation of MF Global, told the committee.

MF Global employees could face civil or criminal penalties if rules or laws were violated, Sommers said.

"They are subject to civil prosecution under our rules, and there would also be potential for criminal violations," Sommers said.