Mr. Sullivan, WorldCom's former chief financial officer, and Mr. Myers, former controller, surrendered around 7 a.m. EDT Thursday at an undisclosed location and were being held by the Federal Bureau of Investigation in Manhattan pending a court appearance.

"They are here and they are in custody," said FBI spokesman Jim Margolin.

Messrs. Sullivan and Myers were criminally charged with conspiracy to commit securities fraud. The two men also were charged with an additional count of securities fraud and five counts of making false filings with the Securities and Exchange Commission, according to a criminal complaint unsealed Thursday in Manhattan federal court.

Criminal charges haven't been filed against the company. If prosecuted, WorldCom's chances for survival could be severely hampered. Already, the company faces civil fraud charges filed by the Securities and Exchange Commission.

The complaint portrays Mr. Sullivan as the architect of the fraud scheme, with Mr. Myers allegedly acting under his orders to transfer billions of dollars in expenses to various other accounts on WorldCom's ledger.

Specifically, Mr. Myers is charged with directing employees of WorldCom's general accounting department to transfer certain line costs from the income statement to the capital expenditure accounts of the company's balance sheet.

"Contrary to WorldCom's usual practices and prevailing accounting industry norms, no documentary support existed for any of these entries," Paul J. Higgins, a special agent with the Federal Bureau of Investigation, alleges in the complaint.

The complaint charges the two executives with submitting false filings to the SEC for the first three quarters of 2001, fiscal 2001, and the first quarter of 2002.

Attorneys for Mr. Sullivan have spoken with prosecutors in recent days. As of late Wednesday, people familiar with the planned case said they didn't believe that a plea deal had been achieved at that point.

A negotiated plea would save the government the time and expense of going to trial and could, potentially, turn Mr. Sullivan into an important witness against others, including Bernard Ebbers, WorldCom's ousted chief executive. It isn't clear whether lawyers for Mr. Myers attempted to negotiate a plea agreement. Mr. Ebbers's attorney couldn't immediately be reached for comment.

WorldCom disclosed on June 25 that it hid $3.8 billion in expenses and falsely posted profits over a five-quarter period beginning in early 2000. The Securities and Exchange Commission has already filed civil fraud charges against WorldCom and is continuing to investigate the company, as are both houses of Congress. Internal documents provided to the SEC show that Messrs. Sullivan and Myers were told two years ago that the accounting treatment they were using was questionable. Two WorldCom employees raised the concerns, the documents show.

Messrs. Sullivan and Myers were dismissed in June after the company's admission that it inflated earnings.

WorldCom filed for protection under Chapter 11 of U.S. bankruptcy code on July 21 in the largest such filing in U.S. history.

U.S. Bankruptcy Judge Arthur Gonzalez approved $2 billion in financing to keep WorldCom operating as it reorganizes its finances. He also granted the Justice Department's request for an independent examiner to ensure an honest accounting of the company's value and investigate for mismanagement, irregularities and fraud.