Troubled Enron Corp. said Thursday it has secured $1 billion in new financing, using its natural gas and pipeline assets as collateral. But its stock price took another dive after rising a day earlier on takeover speculation.

Enron shares closed Thursday on the New York Stock Exchange at $11.99, down $1.91, or 13.7 percent. They have fallen 65 percent since Oct. 16, when Enron said it would take $1.01 billion in charges for certain investments. The shares hit a nine-year low on Tuesday.

After dropping to a nine-year low on Tuesday, shares of the nation's largest natural gas and power marketer rose 25 percent Wednesday amid speculation the Houston-based company was a takeover candidate.

But after the stock market closed for the day, Enron announced the Securities and Exchange Commission had opened a formal investigation into possible conflicts of interest.

The SEC is apparently looking into dealings Enron had with partnerships led by its former chief financial officer, Andrew Fastow, who was forced out last month as investors fled because of questions about the arrangements.

On Thursday, Enron announced its investment bankers had arranged for $1 billion in fresh credit lines that it planned to use partly to refinance maturing debts.

``This is yet another step in our efforts to enhance market and investor confidence,'' said Jeffrey McMahon, Enron's new chief financial officer. ``We are moving aggressively to strengthen our balance sheet and maintain our investment grade credit rating.''

Late Wednesday, Enron said it created a special committee headed by University of Texas law school dean William Powers to respond to the SEC investigation. Powers also was elected to Enron's board of directors.

``I have asked the board to take this action to address fully and forthrightly investors' questions and concerns,'' said Enron chairman and chief executive Kenneth L. Lay. ``We will also make every appropriate public disclosure during the course of the SEC's investigation.''

However, Duane Grubert, an analyst with Sanford C. Bernstein and Co. in New York, said Enron still has much to do to restore investor confidence.

``With (stock) values this low, you've got two camps of investors: guys that hate Enron and guys that want to be cautiously attracted to Enron,'' Grubert said. ``It's led to the trading range being irrationally low and shares being oversold. It's not something the company wants.''

Enron's stock has skidded since the company reported a $638 million third quarter loss just over two weeks ago, dragged down by a one-time charge of $1.01 billion attributed to various losses. Some of these losses have been tied to partnerships managed by Fastow, who was ousted last week.

Earlier this week, Moody's Investors Service downgraded the company's long-term debt and warned of possible further downgrades.

Since reporting its disappointing third quarter, Enron had been negotiating to establish new credit lines.

Carol Coale, an analyst with Prudential Securities Inc. in Houston, said Wednesday's stock price surge, after two weeks of selling, was likely a reaction to a The Wall Street Journal report on rumors of a possible takeover of Enron.

Others might have been buying figuring the stock had hit bottom, she said.

On Tuesday, Enron's stock closed at $11.16, its lowest level since 1992.

Potential buyers include General Electric's GE Capital unit, Warren Buffett's Berkshire Hathaway and Royal Dutch Shell, the Journal said.