NEW YORK (Reuters) - Wall Street shares plunged on Monday as investors fled technology stocks amid resurgent trade war worries, with key indexes trading below their 200-day moving averages and the S&P 500 closing below that pivotal technical level for the first time since Britain’s vote to leave the European Union in June 2016.

The first trading day of the second quarter began with a broad selloff concentrated in the technology and consumer discretionary sectors, as losses by Amazon.com AMZN.O, Tesla TSLA.O and Microsoft MSFT.O, among others, took center stage from retaliatory trade measures China unveiled on Sunday.

With the S&P 500 in a 10 percent correction from its record high in late January, investors were increasingly concerned a nine-year bull market might be in danger of ending.

“It’s more complicated than just a tech selloff. What’s hurting everything is that the S&P went through its 200-day moving average,” said Brian Battle, director of trading at Performance Trust Capital Partners in Chicago. “That attracts momentum sellers and they don’t care what the fundamentals are.”

The Dow Jones Industrial Average .DJI fell 458.92 points, or 1.9 percent, to end at 23,644.19 after dipping below its 200-day moving average. The S&P 500 .SPX fell 58.99 points, or 2.23 percent, to 2,581.88 and the Nasdaq Composite .IXIC dropped 193.33 points, or 2.74 percent, to 6,870.12.

Amazon.com AMZN.O was the biggest drag on the S&P 500, down 5.2 percent, as President Donald Trump continued his twitter attacks on the online retailer.

All 11 major sectors of the S&P 500 closed lower, with the biggest losses seen by the consumer discretionary .SPLRCD and technology .SPLRCT indexes, which were down 2.8 percent and 2.5 percent, respectively.

The tech-heavy Nasdaq was dragged lower by Microsoft MSFT.O, Intel INTC.O, Apple Inc AAPL.O, Facebook FB.O and Alphabet GOOGL.O.

Shares of Tesla Inc TSLA.O ended the day down 5.1 percent after the company was reported to be making 2,000 Model 3s per week, missing its 2,500 target.

The electric automaker’s losses extend last week’s near 14-percent decline as investigations of a fatal California crash and a Moody’s credit downgrade weighed on the stock.

Health insurer Humana Inc's HUM.N shares closed up 4.4 percent on news it was in talks with Walmart WMT.N to expand their partnership or possibly be acquired by the retailer. Walmart stock fell 3.8 percent.

U.S. Treasury yields US10YT=RR fell to two-month lows as investors fled sliding stocks for safety ahead of Friday's closely watched jobs report.

Declining issues outnumbered advancing ones on the NYSE by a 4.17-to-1 ratio; on Nasdaq, a 4.14-to-1 ratio favored decliners.

Slideshow ( 2 images )

Volume on U.S. exchanges was 7.71 billion shares, compared to the 7.29 billion average over the last 20 trading days.