NEW YORK ? Commodities broker Refco Inc., struggling with daily revelations in an accounting scandal, said it will freeze customers? accounts in one of its subsidiaries for 15 days because the unit may not have enough cash on hand to operate normally.

The news, coming one day after Refco?s chief executive was indicted on federal securities fraud charges, prompted the New York Stock Exchange to halt trading in Refco?s stock, which may become a permanent delisting if the company doesn?t give investors more information on its finances.

In addition, the company?s credit ratings were slashed, with Standard & Poor?s warning that there was ?substantial doubt? about the entire company?s liquidity.

And analysts said that while its other subsidiaries appear to be running normally, Refco?s customers ? which include a number of hedge funds involved in Refco?s main derivatives and futures trading ? may decide to move their accounts elsewhere.

Refco does business in the US, Canada, Bermuda and Europe. The company lists its Bermuda office as a private mail box at 48 Par-la-Ville Road, the offices of Mailboxes Unlimited.

And a call to the Bermuda office yesterday was patched through to the company?s Chicago office. When asked who was the appropriate person to contact in the Bermuda office, the call was disconnected.

Refco?s largest shareholder, buyout firm Thomas H. Lee Partners LP, was one of the founding investors in Bermuda insurance companies established in 2001: Axis Capital Holdings and Endurance Specialty Holdings.

Refco was already under investigation by the US Securities and Exchange Commission for its role in short-selling shares in Sedona Corp., a software maker.

Short sellers bet on drops in stock prices. Bermuda investment firm Lines Overseas Management is also under SEC investigation related to Sedona Corp., including allegations of fraud and market manipulation.

?Refco?s main business is really its prime brokerage for futures trading,? said Denise Valentine, senior analyst at Celent, a financial consulting group.

?Most of its business and customers are probably unaffected by this freeze. But it?s going to cast a long shadow over the entire company. If you?re a customer, you have to be thinking about a backup plan.?

The frozen accounts are held by Refco Capital Markets Ltd., an unregulated offshore broker for stocks, bonds and currencies that former CEO Phillip Bennett, 57, allegedly used to help hide up to $545 million in bad debts.

The Justice Department on Wednesday charged Bennett with allegedly causing Refco to file fraudulent statements to securities regulators because of his activities. He is free on a $50 million bond.

In a statement, Refco said it would put a 15-day moratorium on all the unit?s transactions ? effectively preventing customers from withdrawing money from their accounts ? ?to protect the value of the enterprise?.

A spokesman for Refco did not immediately know how many accounts or how much money would be frozen. While Refco?s regulatory filings do not list revenues from each subsidiary, the company?s statement said Refco Capital Markets ?represents a material portion of the business of the company.?

Other subsidiaries have enough liquidity to keep operating normally, the company said.

Those regulated subsidiaries deal in futures commissions, derivatives and commodities, and are considered the company?s main line of business.

The wave of bad news prompted the Chicago Mercantile Exchange, the nation?s largest futures exchange, to issue a statement saying that Refco, a major customer of the Merc, remains in good standing there, and that the Merc has a framework of oversight and regulation to protect investors.

Shares of Chicago Mercantile Exchange Holdings Inc. nonetheless fell $8.60, or 2.7 percent, to $310.40 on the New York Stock Exchange.

Shares of Refco fell $2.95, or 27 percent, to $7.90 on the NYSE before they were halted prior to the company?s announcement.

The NYSE announced that the halt would continue while it evaluates whether the company needs to make further disclosures or even if it can continue to be listed on the Big Board.

Refco?s bond and credit ratings suffered new downgrades on the news. ?Standard & Poor?s believes that there is substantial doubt concerning the liquidity of Refco,? the credit rating agency said in a statement.

S&P lowered Refco?s counterparty credit rating from B-plus to B-minus, while Refco?s own corporate bonds were lowered from B-minus to CCC.

All the new ratings put Refco?s debt firmly within ?junk? status, considered to be speculative and more likely to default.

The capital markets subsidiary is at the centre of the accounting troubles at Refco.

Bennett is accused of moving uncollectable debts in and out of that subsidiary, and other entities, to hide that the company was counting debts as revenues, even though it realistically was unlikely to collect on those debts.

Refco announced the irregularities on Monday, placing Bennett on leave after he repaid $430 million with interest to the company. Santo Maggio, head of Refco Capital Markets Ltd. and Refco Securities LLC, also was placed on leave.

In its statement, Standard & Poor?s noted that the money Bennett repaid the company might not immediately be available. Bennett?s lawyer said Wednesday the former CEO obtained the money through a bank loan secured by his Refco stock.

The company first went public in August, and federal prosecutors said Bennett?s alleged transactions hid the true value of the company from investors.

The company has said that its earnings reports dating back to 2002 are unreliable.

To help Refco cope with its sudden troubles, the company has retained former Securities and Exchange Commission Chairman Arthur Levitt and Eugene Ludwig, CEO of Promontory Financial Group LLC, as special advisers to the board of directors.