More than $1.2 billion in assets appears to be missing from customer accounts at bankrupt broker-dealer MF Global, the bankruptcy trustee in charge of making accountholders whole, stated Monday.

That amount, likely more than twice the size of the estimated $633 million hole the trustee had previously talked about, represents more than 22 percent of the $5.45 billion reportedly held in customer assets the day the firm went bankrupt.

"At present, the trustee believes that even if he recovers everything that is at U.S. depositories, the apparent shortfall in what MF Global management should have segregated at U.S. depositories may be as much as $1.2 billion or more," said James Giddens, the trustee for MF Global, in a statement Monday. "The trustee wants to stress that these are preliminary numbers that may well change, and the trustee will update in due course."

In the statement, Giddens also noted the trustee was close to exhausting the disbursement of funds recovered so far, and that, while additional funds had been identified as being held overseas, "it has been his experience that recovery of these foreign assets may take more time."

The funds missing from MF Global's customer accounts appear to have been used by the firm in a desperate, highly illegal bid to survive during its final weeks by dipping into consumer accounts. While nothing has been proven definitely, there's been speculation the firm used those funds to cover margin calls on counter-party positions or to post collateral on an emergency lifeline loan.

Before Monday's announcement, some had speculated the MF Global shortfall might be bigger than reported. On Nov. 2, finance blog Zero Hedge noted the Chicago Mercantile Exchange--where MF Global plied futures and commodities trading on behalf of its clients--said it had held "segregated funds on deposit" of some $2.5 billion and "clearing-level segregated collateral" of $1.5 billion on behalf of MF's clients. Quick math suggests that leaves a hole of $1.45 billion, even larger than the $1.2 billion figure reported Monday.