The stock market sell-off on Wall Street intensified Wednesday, knocking the Dow down more than 600 points and wiping out the gains for the year for the blue-chip average and the broad Standard & Poor's 500 index.

Technology stocks, which had been the best-performing part of the market earlier in 2018, suffered the biggest declines. The Nasdaq composite, home to many of the market's most popular tech stocks, plunged 4.4 percent, pushing it down 12.3 percent from its late August high and deeper into official "correction" territory.

The latest swoon, which knocked the S&P 500 down more than 3 percent Wednesday, signaled to many Wall Street pros that the decline was entering a new, more dangerous phase. There's growing concern now that this decline is more than a garden variety pullback, or drop of 5 percent to 9.99 percent, and could morph into a drop of 10 percent of more for the broad market.

"With the big sell-off today, the market may have moved from pullback into correction territory," says Nick Sargen, chief economist and senior investment advisor for Fort Washington Investment Advisors.

Read more in the Milwaukee Journal Sentinel.