Sell-off continues after hours — S&P 500 futures now down 6% on the day

S&P 500 futures were trading below the lowest level hit earlier in the stock market during Monday’s wild sell off.

The S&P 500 was down 113 points, or 4.1 percent Monday in its worst day since August, 2011. The futures, which typically match the spot market’s decline, were down even more, off by 5.3 percent as of 4:36 pm ET.

The cash S&P 500, which closed at 2,648, touched 2,638 in afternoon trading, and that is the level traders are watching to see if it can act as support or signal more selling. The S&P futures were down 143 points at 2,611 in late afternoon trading, 27 points below the cash market low.

In the futures market, it was signalling selling.