Stocks have stepped up their selling in the final hour of trading. The Dow Jones industrial average is off more than 600 points, dropping below the 9,000 mark for the first time in five years.
Financial, energy and health care stocks led the decline Thursday. General Motors Corp. led the Dow lower, falling nearly 30 percent.
The Dow is down 645.62, or 6.97 percent, to 8,612.48. The blue chips hadn't fallen below the 9,000 level since Aug. 6, 2003.