Regulators had previously thought the firm was using customer funds on the Thursday and Friday before it filed for bankruptcy on October 31.
CME Group, the Chicago exchange where MF Global traded, said it had reviewed the company's books a week before the bankruptcy and found no issues with the customer money.
If MF Global started improperly dipping into its customers' accounts long before the firm's collapse, the allegation would raise questions of why the regulators and auditors failed to spot such behavior.
Congress has already started asking questions about potential lapses in regulatory oversight of MF Global. The pressure on regulators would only increase if MF Global turns out to have misused customer funds over an extended period of time.
"Establishing the specifics of what happened is key to figuring out how the system failed and how to fix it going forward," Republican Senator Chuck Grassley of Iowa said in a statement on Thursday. "Congress will need to keep drilling down."
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Investigators such as the Commodity Futures Trading Commission have been scouring the company's books, described as messy and unorganized, for the fund shortfall that has been estimated as much as $1.2 billion by the liquidating trustee..
However, regulators have been at odds with the trustee, believing that figure is too high.



