As MF Global careened toward bankruptcy in October, the brokerage firm used customer funds to bankroll its business, apparently assuming that the money would be put back by the end of each day, a trustee overseeing the firm’s liquidation reported Monday.

But by the end of the day on Oct. 26, five days before MF Global sought bankruptcy protection, the firm came up short, the trustee reported. That was days before regulators were alerted to the shortfall, according to earlier accounts.

Now, an estimated $1.2 billion of customer money is missing.

It remains to be seen whether the money can be recovered, trustee James W. Giddens said in an update on his investigation of MF Global’s collapse.

In a frenzy of trading, much of the money flowed through MF Global’s banks and was scattered among recipients such as banks, exchanges, MF Global affiliates and counterparties to trades, the trustee said.

It has not been determined “whether there is a sound and legal basis for recoveries against third parties that will help make customers whole,” Giddens wrote.

The analysis involves “complex factual and legal questions,” he wrote.

The implosion of MF Global left many customers in a financial bind and has shaken confidence in the brokerages on which commodity investors depend.

It also has tainted the reputation of Jon S. Corzine, the former New Jersey governor, U.S. senator and Goldman Sachs boss who presided over MF Global’s unraveling.

Corzine tried to turn the firm around by placing big bets on European debt, and he has defended those investments in testimony to Congress. But Giddens said those trades contributed to the drain on MF Global’s resources by triggering margin calls.

The firm imploded as a big quarterly loss was followed by credit downgrades and the equivalent of a run on the bank when customers rushed to withdraw their funds.

Before its fatal crisis, MF Global had tapped customer funds in increments of less than $50 million, but as the firm’s need for cash grew, “much larger amounts were used,” the trustee said.

Although there was a shortfall in customer accounts as early as Oct. 26, MF Global employees “may not have been immediately aware of it,” the trustee said.

In the week before the bankruptcy, MF Global’s trading became so chaotic that the firm’s workers and employees “had difficulty keeping up,” the trustee said. “A number of transactions were recorded erroneously or not at all.” The trading involved more than $200 billion in cash and securities, the trustee said.

The trustee has not yet determined whether any regulations were violated, spokesman Kent Jarrell said.

The Justice Department and various regulators have been investigating.