Another plunge in the price of oil is driving stocks sharply lower in afternoon trading.
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Energy stocks slumped as the price of crude briefly dipped below $50 a barrel.
The Dow was down 295 points, or 1.7 percent, to 17,539 as of 12:43 a.m. Eastern time. It was down as much as 315 earlier.
The Standard & Poor's 500 index fell 33 points, or 1.6 percent, to 2,024. The Nasdaq composite fell 56 points, or 1.2 percent, to 4,671.
Energy companies had the worst declines in the S&P 500 index. Denbury Resources and Noble Energy each lost 9 percent.
The euro sank to a nine-year low as traders worried about whether Greece will stay in Europe's currency union.