By Victor Reklaitis and Carla Mozee, MarketWatch

NEW YORK (MarketWatch) -- U.S. stocks slumped Thursday, led by the tech sector, slapping the major benchmarks with their biggest one-day loss in almost two months.

Why the drop? Strategists said there wasn't one single explanation. Market observers, however, pointed to some possible drivers including Apple Inc.(AAPL), whose own shares were down more than 3%. Other worries centered on the Russia-Ukraine and Mideast conflicts as well as a weak U.S. durable-goods report. Strategists also cited divergences between suffering small-cap stocks and the broader market and technical factors, including the S&P 500's slicing through its 50-day moving average.

The S&P (SPX) slid 32.31 points, or 1.6%, to finish at 1,965.99. All S&P sectors endured losses.

The Dow Jones Industrial Average (DJI) also took a hit, falling 264.26 points, or 1.5%, to close at 16,945.80.

Both the S&P 500 and Dow suffered their biggest drops since July 31, when they fell 2% and 317 points, respectively. That's after both achieved record closes last week.

The technology sector was a particularly hard-hit area, faring worst among S&P sectors, and the tech-heavy Nasdaq Composite (RIXF) declining by 88.47 points, or 1.9%, to end at 4,466.75. The Nasdaq's loss also was its largest since July 31.

Worries about durables, geopolitics: Orders for durable U.S. goods plunged a record 18.2% in August after a record 22.5% gain in July, mainly because of volatile demand for airplanes. Economists surveyed by MarketWatch had expected orders to fall 17.3%.

The headline number for durable goods may have spooked some investors, according to Doug Coté, chief market strategist at Voya Investment Management. In addition, the report's encouraging details, such as what it said about underlying business investment, could put more pressure on the Federal Reserve to raise interest rates, he argued. (Read more: Early days of a rate hike are characterized by stock weakness: http://www.marketwatch.com/story/get-ready-for-rising-interest-rates-and-stocks-2014-09-25.)

Then there's the matter of international conflict. "Geopolitical risks have been overlooked, but the longer they go on without resolution, the more concerning it gets," Cote noted.

Iraq's prime minister warned about plots by the Islamic State to launch attacks on subway systems in New York City and Paris on Thursday -- highlighting rising concerns about terrorist organizations' growing global threat.

Meanwhile in Russia, courts there could receive the OK to seize foreign assets under a draft law intended as a response to Western sanctions over the Ukraine crisis, a Reuters report said Thursday.

In other economic news, weekly jobless claims rose to 293,000, while economists surveyed by MarketWatch had expected claims to rise to 300,000.

Check out a recap of MarketWatch's stock market live blog

Movers and shakers: Shares in Apple dropped Thursday after the company pulled an update to iOS 8 on Wednesday. Users had reported major problems with the operating-system update, and Apple also is dealing with complaints about the iPhone 6 Plus being susceptible to bending. Check out: Apple's PR nightmare has turned into a social-media joke.

The tech titan's slide of 3.8% was the second-worst performance in the S&P 500, exceeded only by Allegheny Technologies Inc.'s(ATI) 4.8% tumble.

(Read more about the day's notable stock moves here http://www.marketwatch.com/story/jabil-nike-micron-in-spotlight-2014-09-25.)

Other markets: Japan's Nikkei Average surged 1.3% as the yen weakened. Meanwhile, the euro (EURUSD) hit its lowest level against the dollar since 2012 after European Central Bank President Mario Draghi said the bank stands ready to launch more stimulus measures to boost growth.

European stocks were dragged down by U.S. losses after initially gaining following Draghi's comments. Gold futures(GCZ4) rose.

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