NEW YORK—Wall Street’s angst over the ongoing fallout from the credit crisis made for a turbulent end to a volatile week Friday—stocks tumbled, soared and then turned south again as investors tried to assess the dangers faced by the country’s biggest mortgage financiers, Fannie Mae and Freddie Mac.

The Dow Jones industrial average, which traded down more than 250 points in the session, briefly moved into positive territory Friday before ending down more than 125 points. The blue chips also traded below 11,000 for the first time in two years. And all the major indexes ended with another losing week.

A new high for oil prices above $147 a barrel also weighed on stocks.

The fate of the government-chartered companies was a focus of trading Friday as it had been earlier in the week. Shares of Fannie Mae and Freddie Mac fell sharply over several sessions on concerns about their stability. Wall Street is worried that a collapse of the two financiers would cause further shock to the financial system, and trigger more losses to banks and brokerages with significant holdings of mortgage-backed securities.

The well-being of Fannie Mae and Freddie Mac is crucial because they hold or guarantee about $5 trillion worth of mortgages, or about half the outstanding mortgages in the United States. Their troubles are just the latest depressing turn in a year-old credit crisis that shows no sign of ending, disappointing some stock traders who thought just months ago that the worst was perhaps over.

Stocks fluctuated late in the session amid varying reports that the Federal Reserve could aid Freddie Mac and Fannie Mae.

Sen. Christopher Dodd, D-Conn., the Senate Banking Committee chairman, raised the prospect that the companies could be given access to emergency Federal Reserve lending. Dodd, who spoke Friday to Fed Chairman Ben Bernanke and Treasury Secretary Henry Paulson, said the two are “looking at various options” for propping up the firms if they ultimately need help. Those include giving them access to the Fed’s emergency lending “discount window,” Dodd said.

But a Fed spokeswoman said later the central bank had not talked with Fannie and Freddie about the emergency lending program. She declined to discuss any other options being considered.

Earlier this year, the Federal Reserve took the unprecedented step of offering direct loans to investment banks from its discount window.

Some observers noted that Freddie Mac and Fannie Mae weren’t short of cash, but of access to capital.

“The issue is who is going to make good on the long-term debt, not who is going to provide them with short-term cash,” said Jerry Webman, chief economist at Oppenheimer Funds Inc. in New York.

“It started with housing but it’s now turning into this issue of availability of capital,” he said of the overall problems in the financial sector.

The concerns left the Dow down 128.48, or 1.14 percent, to end at 11,100.54 after having fallen to 10,977.68. It last traded below 11,000 on July 25, 2006.

Broader stock indicators also logged declines. The Standard & Poor’s 500 index fell 13.90, or 1.11 percent, to 1,239.49, and the Nasdaq composite index fell 18.77, or 0.83 percent, to 2,239.08.

Friday’s drop meant Wall Street moved squarely into a bear market, which is defined as a 20 percent drop from a recent peak. The Dow is down 21.6 percent from the record closing high of 14,164.53 it reached in October. The S&P 500 is down 20.8 percent and the Nasdaq is off 21.7 percent.

For the week, the Dow fell 1.67 percent, the S&P 500 lost 1.85 percnet and the Nasdaq declined 0.28 percent. It was the fourth straight weekly decline for the Dow and the sixth consecutive weekly decline for the S&P 500 and the Nasdaq.

The market’s other trouble spot, oil, continued its ascent, rising to a trading record of $147.27 amid tensions between the West and Iran. Light, sweet crude for August delivery settled up $3.43 at $145.08, slightly below a record close of $145.29 a barrel set more than a week earlier.

Bond prices fell sharply as investors worried a bailout of Fannie Mae and Freddie Mac could dent the government’s credit rating. Ordinarily, bonds are seen as a safe haven during stock market pullbacks. The yield on the benchmark 10-year Treasury note, which moves opposite its price, rose to 3.96 percent from 3.80 percent late Thursday. The dollar was mixed against other major currencies, while gold prices rose.

Worries about financials dominated trading. Freddie Mac fell 25 cents, or 3.1 percent, at $7.75, after trading as low as $3.89 in the session. Fannie Mae tumbled $2.95, or 22 percent, to $10.25 after trading as low as $6.68.