NEW YORK (CNNMoney.com) - Stocks sank Friday, sending the Dow Jones industrial average tumbling more than 200 points and putting the world's most widely watched stock index into the red for the first time in 2006.

Disappointing results from big household names like General Electric and Citigroup (as well as Yahoo!, Apple and Intel earlier in the week) have raised concerns about corporate profits in 2006, Art Hogan, chief market strategist at Jefferies & Co, said.

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In addition, crude oil jumped $1.52, or over 2 percent, to $68.35 a barrel as tensions mounted over Iran's nuclear ambitions, adding to the jitters on the Street.

The 30-share Dow industrials (down 213.32 to 10,667.39, Charts) and the broader S&P 500 index (down 23.55 to 1,261.49, Charts) tumbled nearly 2 percent, the biggest one day point-loss for both indices since March, 2003.

The tech-heavy Nasdaq composite (down 54.11 to 2,247.70, Charts) skidded 2.4 percent, the biggest one day point-loss since Sept., 2003.

For the week, the Dow, S&P and Nasdaq all closed lower.

The market had gotten off to a fast start in the new year, with the Dow industrials and S&P 500 gaining for six out of seven sessions and hitting 4-1/2 year highs. The Nasdaq gained seven in a row and hit a nearly 5-year high.

GE (down $1.31 to $33.37, Research) reported fourth-quarter profit fell 46 percent, in line with Wall Street expectations, and raised the lower end of its 2006 guidance. But revenue for the quarter was below forecasts and shares fell 4 percent.

Shares of Dow component Citigroup (down $2.25 to $45.69, Research) sank close to 5 percent after the bank said fourth-quarter earnings from continuing operations fell 3 percent.

Motorola (Research) added to earnings worries. The world's second-largest mobile phone maker reported fourth-quarter earnings up about 86 percent from last year but indicated that first-quarter earnings and revenue will fall, sending shares down almost 8 percent.

Shares of Xilinx (down $2.40 to $27.39, Research) sunk 8 percent on news that the semiconductor maker posted a 26 percent rise in third-quarter profit but its forecast disappointed investors.

Supertex (down $11.76 to $31.49, Research) tumbled 27 percent after the semiconductor maker posted a higher third-quarter profit but fell short of Wall Street estimates.

Other chip stocks fell in sympathy, sending the Philadelphia Semiconductor index, or the SOX, down over 4 percent. (For more on the tech sector, click here.)

Key earnings reports are expected next week from other big-name companies, including American Express (down $1.19 to $51.40, Research), Texas Instruments (down $0.84 to $31.66, Research) and Microsoft (down $0.61 to $26.41, Research).

In other news, shares of Google (down $36.98 to $399.46, Research) plummeted 9 percent, its largest one-day loss ever, on news the Internet giant is fighting a subpoena from the Justice Department asking it to turn over search records in an effort to defend a child pornography law. (Full story.)

Shares of Ford (down $0.32 to $7.90, Research) fell 4 percent ahead of the automaker's announcement about its restructuring plan. (Full story.)

Persistent rumors that Walt Disney (down $0.52 to $25.72, Research) may be looking to acquire Pixar (down $0.41 to $58.46, Research) dragged shares of both companies lower.

General Electric and Japan's Hitachi may have joined forces to make a $3.5 billion bid for nuclear-technology company Westinghouse Electric, according to a report in the Wall Street Journal.

And Albertsons (up $0.24 to $24.11, Research) said it received an offer from a consortium seeking to purchase the company and is negotiating with the group.

Market breadth was negative. On the New York Stock Exchange, losers beat winners more than two to one on volume of 2.1 billion shares. On the Nasdaq, decliners topped advancers by nearly three to one on volume of 2.4 billion shares.

Consumer sentiment improved in early January on steady energy prices, better job conditions, and hefty stock gains in early 2006, according to the University of Michigan's report.

Treasury prices rose, lowering the yield on the 10-year note at 4.34 percent. The yield on the 2-year note stood at 4.35 percent, indicating an inverted yield curve.

The yield curve, which refers to the slope of rates in the Treasury market, briefly inverted in late December when the two-year note yield exceeded the 10-year yield, a rare occurrence that often bodes badly for the economy.

The dollar edged lower against the euro and the yen.

COMEX gold fell $5 to $554 after hitting a 25-year high amid concerns about the economy, high oil prices and geopolitical tensions.

Asian markets ended virtually unchanged after a week of market slides due to the investigation into the high-flying Internet company Livedoor. European stocks ended lower after trading just below 4-1/2-year highs earlier in the session.