U.S. markets staged a sweeping U-turn Monday as a battered technology sector again helped lead the decline.

The Dow Jones industrial average swung nearly 800 points, from 250 points up to almost 500 points into negative territory, wiping out its gains this year as last week’s gyrations carried over to Monday.

The nosedive gained momentum during the last hour of trading.

“This is the kind of response you see in financial markets when the real economy, profits, wages and growth, becomes more uncertain,” said Douglas Holtz-Eakin, president of the American Action Forum and former economic adviser to the late Sen. John McCain. “And it has become more uncertain from a policy point of view, around trade and the Federal Reserve. People are bouncing around on those. But the global growth outlook has become more uncertain as well. There is a slowdown in some major economies, China, Russia and some of Europe. And the emerging markets are in trouble.”

The Standard & Poor’s 500-stock index erased its 2018 gains as well and the tech-heavy Nasdaq composite plunged deeper into the red. The Nasdaq was already in correction territory, which is more than 10 percent off its high.

Several major industrial stocks were down, including oil giant Chevron, Visa, United Technologies and Visa.

All the FAANG stocks – Facebook, Amazon, Apple, Netflix and Google-parent Alphabet – were in the red Monday as the Nasdaq sloped downward by 100 points, or about 1.4 percent. Amazon.com. was down more than 8 percent.

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