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.

MF Global filed for bankruptcy protection after risky bets on some of Europe's most indebted countries. Sommers said that regulators haven't found evidence that client funds were incorporated in the European debt positions.

Under current rules, customer money is supposed to be kept segregated from the firms' accounts, and daily reports sent to the CFTC.

"We were receiving daily segregation reports from MF Global and those did not raise red flags for us until right before the bankruptcy," Sommers said.

In his statement, Corzine provided details on so-called repurchase-to-maturity transactions that have drawn legal and regulatory scrutiny in the weeks since the bankruptcy. He described himself as a "strong" advocate of the transactions while saying that because he isn't an accountant he can't vouch for the way the transactions were handled.

"I accept responsibility for the RTM trades that MF Global engaged in from the time that I arrived at MF Global until my departure, on November 3, 2011, and I strongly advocated the trading strategy that I have described," he said.

MF Global's board was told of the European debt trades and approved limits on the risk in the trades by specific countries, Corzine said in his statement.

"At the time of the bankruptcy, MF Global was within the risk limits set up by the board of directors," he said. "MF Global's board was not a rubber stamp."

None of the foreign debt securities that MF Global used in the repo transactions has yet defaulted or been restructured, Corzine said.