S&P 500 breaks 1,900 ‘trapdoor,’ where to next?

A trader on the floor of the New York Stock Exchange.
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U.S. stocks plunged Wednesday with the selling accelerating after the S&P 500 broke through a key level technical analysts were watching as support.

With this level gone, watch out below, said these market analysts, who solely study charts to make buying and selling decisions.

"The S&P 500 broke below 1,900 and that triggered a kind of trapdoor effect," Art Cashin, director of floor operations at the NYSE for UBS Financial Services, said on CNBC in reference to the market's drop late Wednesday.

The last traded at 1,900 in early October of last year.

So when will the selling stop? Chart analysts gave us the next levels to watch.