Stocks extended losses in midday trading on Wednesday, with the S&P 500 index briefly falling 1 percent as commodity shares dropped further.

Oil prices slid more than $4 a barrel, dragging down shares of major energy companies. Exxon Mobil Corp was down 2 percent at $70.48.

The Dow Jones industrial average <.DJI> dropped 56.76 points, or 0.62 percent, to 9,039.96. The Standard & Poor's 500 Index <.SPX> fell 7.72 points, or 0.79 percent, to 971.90, after dropping 1.02 percent to a session low at 969.73. The Nasdaq Composite Index <.IXIC> dropped 14.77 points, or 0.75 percent, to 1,960.74.

(Reporting by Caroline Valetkevitch; Editing by Jan Paschal)