The S&P 500 failed to break a key technical resistance level for a second day on Tuesday as low trading volume raised further questions about the strength of the market.

Based on the latest available data, the Dow Jones industrial average <.DJI> was down 6.13 points, or 0.05 percent, to end unofficially at 12,393.90. The Standard & Poor's 500 Index <.SPX> was down just 0.24 point, or 0.02 percent, at 1,332.63. The Nasdaq Composite Index <.IXIC> was up 2.00 points, or 0.07 percent, at 2,791.19.

(Reporting by Caroline Valetkevitch; Editing by Jan Pascshal)