Federal prosecutors yesterday charged Phillip R. Bennett, the ousted chief executive of commodities broker Refco Inc., with a single count of securities fraud in connection with hundreds of millions of dollars in debt they claim he concealed from investors.

Law enforcement authorities named Bennett, 57, in a six-page criminal complaint. They accused him of filing a false report with the Securities and Exchange Commission that made the company's finances appear stronger before the company's August initial public offering. Bennett, who was arrested Tuesday night, was released on bail after a hearing before Magistrate Judge Douglas F. Eaton yesterday.

Michael J. Garcia, the U.S. Attorney for the Southern District of New York, told reporters at a news conference that the investigation into financial irregularities at Refco continues. Authorities are examining whether undisclosed related-party deals, which moved uncollectable debt off the books, helped Refco improve its financial health in advance of the $583 million public offering.

Garcia said investigators had worked "nearly around the clock" since Bennett's "active role" in a scheme to bury debt became public this week. The company's stock price dropped by more than 45 percent after news reports about Bennett and the debt issue, he said.

Gary P. Naftalis, a defense lawyer for Bennett, did not return calls. He told the magistrate judge that the government had "jumped the gun" by arresting and charging his client, according to the Associated Press.

The complaint, signed by U.S. Postal Inspector Heather Tucci, substantially accelerates the fast-moving investigation. Tucci wrote that Bennett, "and others known and unknown," failed to notify investors about Refco's dealings with Refco Group Holdings Inc., a privately held, third-party entity controlled by Bennett.

In the August SEC filing, Refco was supposed to disclose any deals worth more than $60,000 between the company and other entities in which Refco executives had financial interests. Debts incurred by Refco executives to the company also were supposed to be disclosed on the registration statement. Securities rules require insiders to report their dealings with the company to help signal potential conflicts of interest to investors.

On Monday, Refco said it would restate financial reports dating to 2002 because of the disclosures about Bennett and the firm. Refco added that it would delay filing its quarterly report, due next week, because lawyers and forensic accountants hired by the company's audit committee are investigating. Bennett has repaid the company $430 million in debt, plus interest, corporate officials said.

Rob Solomon, a spokesman for Refco, declined to comment yesterday, saying only that the company is cooperating with prosecutors, the Securities and Exchange Commission, the New York Stock Exchange and the Commodity Futures Trading Commission.

Former Refco president Santo C. Maggio is on leave at the request of the company's board of directors. Former chief operating officer William M. Sexton, who had been scheduled to retire, has been named Refco's chief executive.

Bennett faces a maximum of 20 years behind bars if he is convicted of securities fraud, prosecutors said.