Fear returned to Wall Street on Wednesday, pushing the S&P 500 down in another 4 percent drop, triggered by worries that Europe's crisis could engulf French banks and eventually spill onto the U.S. financial sector.

Based on the latest available data, the Dow Jones industrial average fell 521.42 points, or 4.64 percent, to unofficially end at 10,718.35. The Standard & Poor's 500 Index slid 51.91 points, or 4.43 percent, to finish unofficially at 1,120.62. The Nasdaq Composite Index lost 101.47 points, or 4.09 percent, to close unofficially at 2,381.05.