Market check: Will S&P 500 selloff steepen?

Traders work on the floor of the New York Stock Exchange.
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Chart analysts believe the recent breakdown in the S&P 500 has placed the index in a danger zone with potentially bigger losses on the way.

Since reaching a recent high of 2,130 in June, the large-cap S&P index is down 3 percent on growing concerns over the unresolved debt crisis in Greece.

"For weeks, we've been keying on 2,074 on the SP500 E-mini as the first level where real technical damage would occur," said Frank Longman, managing director at Brean Capital.

The S&P 500 E-mini refers to the stock market index futures contract traded on the Chicago Mercantile Exchange's Globex electronic trading platform.