NEW YORK (CNN/Money) - WorldCom Inc. said Monday it defaulted on some loans and that it may have overstated financial results as far back as 1999 as shares of the troubled telecommunications company became all but worthless.

WorldCom stock tumbled 77 cents, or 93 percent, to 6 cents Monday, as investors reacted for the first time to disclosures that the company artificially inflated financial results by hiding nearly $4 billion in expenses.

Monday marked the first day of trading in WorldCom (WCOME: down $0.77 to $0.06, Research, Estimates) stock since the company late last Tuesday became the latest firm to mislead investors with dubious accounting.

More than 1.5 billion WorldCom shares changed hands, a record on the Nasdaq Stock Market, which threatened to delist the company's shares by Friday.

The latest selloff in WorldCom, whose shares once fetched $62, comes as the company told the Securities and Exchange Commission on Monday that it may restate results going back to 1999 and 2000, six days after saying it overstated results for last year and the first three months of 2002.

The company also said it faces delisting of its stock by Nasdaq as of July 5, although it may win a stay of that order. And some of the debt-heavy company's lenders have notified it that it is in default.

The federal government is conducting a review to determine whether it should suspend the right of WorldCom to win any new government business because of allegations the long-distance giant covered up losses. The General Services Administration launched the review after the SEC last week charged WorldCom with fraud.

A WorldCom SEC filing Monday said no conclusion has been reached regarding "material reversals of reserve accounts" in 1999 and 2000. Over the next five quarters the company hid $3.8 billion in expenses, making cash flow and profits look better than they really were.

Former WorldCom CEO Bernard Ebbers

WorldCom warned Monday that some of its lenders had notified the company it is in default of its debt agreements and that lenders holding 51 percent of $2.65 billion in loans now had the right to demand early repayment of that debt. It also was notified that it no longer can sell any new accounts receivable into a $1.5 billion program to turn those into securities.

The company owes about $30 billion to lenders.

"These notifications were anticipated," WorldCom CEO John Sidgmore said. "We are engaged in discussions with lenders regarding replacement facilities and remain optimistic that our good working relationships will ultimately reach a positive resolution."

To stave off bankruptcy, the company has cut 17,000 jobs, or 20 percent of its work force. In addition, WorldCom is trying to sell assets to raise money.

Investigators looking into accounting irregularities at the phone service provider are now focusing on former CEO Bernard Ebbers, according to a published report Monday.

Ebbers, who resigned from the company in April, is expected to be questioned by an investigator hired by the long-distance provider he helped build, as well as by the Securities and Exchange Commission and congressional investigators, according to a story in the Wall Street Journal.

Chief Financial Officer Scott Sullivan was fired by the company Tuesday when it revealed the restatement of results. The Journal said that investigators are questioning how Sullivan's actions could have gone undetected by Ebbers, given his tight control of the company.

Ebbers spoke publicly about the accounting problems at WorldCom on Sunday at his church in Brookhaven, Miss., his longtime home, the Journal said. It reported that at the end of the Sunday service he spoke to congregation and said, "I want you to know you aren't going to church with a crook."

The paper said that he told the congregation that he had gotten a call on Tuesday about the problems at WorldCom.

"I don't know what the situation is with all that has been reported. I don't know what is going to happen or what mistakes have been made," the paper quotes him as saying.

"No one will find me to have knowingly committed fraud," he added.