Stocks slumped at the open on Thursday after a rating agency downgrade of Spain rekindled concerns over euro zone debt problems and disappointing economic data from China and the United States heightened global growth worries.

The Dow Jones industrial average was down 167.03 points, or 1.37 percent, at 12,046.06. The Standard & Poor's 500 Index was down 19.31 points, or 1.46 percent, at 1,300.71. The Nasdaq Composite Index was down 41.51 points, or 1.51 percent, at 2,710.21.