Trigger-happy investors dumped U.S. stocks on Thursday, scared out of the market by a sudden fall through a key technical level brought on by more worries about Europe's debt troubles.

Based on the latest available data, the Dow Jones industrial average <.DJI> was down 134.26 points, or 1.13 percent, at 11,771.33. The Standard & Poor's 500 Index <.SPX> was down 20.54 points, or 1.66 percent, at 1,216.37. The Nasdaq Composite Index <.IXIC> was down 50.29 points, or 1.91 percent, at 2,589.32.

(Reporting by Caroline Valetkevitch; Editing by Kenneth Barry)