The S&P 500 dropped 1.7% after careening between an early gain of 1% and a loss of 2.3%, sinking further from its all-time high set a week ago. The Nasdaq composite was 2.9% lower, and the Dow Jones Industrial Average was down 408 points, or 0.8%, as of 1 p.m. Eastern time.

Indexes swung lower as companies selling computer chips, memory and other building blocks of the AI boom broke from early gains to losses. Micron Technology went from a jump of 4.2% to a drop of 7.6%, for example. That’s a day after it soared 9.9% and two days after it plunged 13.3%.

The computer memory company’s stock has already tripled so far this year, raising criticism that it’s gone too far, too fast. Following last week’s industrywide sell-off, the question is whether AI stocks broadly are heading for a long downturn or just needed a shake-out to get rid of excessive optimism.

Marvell Technology dropped 13.3%, and Advanced Micro Devices sank 8.7% after both AI winners also erased early-morning gains. Nvidia’s fall of 3.1% was one of the heaviest weights on the S&P 500 because the chip company is Wall Street’s largest company by value and thus its most influential.

All the while, several big-name AI companies are racing to list their stocks on a U.S. exchange and sell them at high prices. OpenAI, the maker of ChatGPT, said Monday it was the latest to file confidential paperwork with U.S. regulators for an initial public offering. SpaceX’s IPO could happen later this week.

The weakness for AI stocks drowned out the benefit Wall Street got from easing oil prices. More stocks in the S&P 500 actually rose than fell, despite the sharp drop for the overall index, as the price for a barrel of Brent crude oil sank 2.7% to $91.66.

Oil prices have swung as hopes rise and fade that the United States and Iran can reach a deal to reopen the Strait of Hormuz. A reopening would allow oil tankers to resume delivering crude from the Persian Gulf to customers worldwide.

Oil prices pared their losses, though, after President Donald Trump said Iran was responsible for downing an American military helicopter near the Strait of Hormuz and that the United States “must” respond to the attack.

High oil prices caused by the war with Iran have already created a painful acceleration of inflation for U.S. shoppers. They have also pushed bond yields higher worldwide, raising the pressure on stock prices.

Treasury yields eased a bit Tuesday with the fade in oil prices. The yield on the 10-year Treasury fell to 4.54% from 4.56% late Monday. But it’s still well above its 3.97% level from just before the war with Iran.

The latest monthly updates on U.S. inflation will arrive later in the week, with one on consumer prices coming Wednesday and one on wholesale prices coming Thursday.

Inflation is high enough, and the U.S. job market looks strong enough, that traders on Wall Street largely expect the Federal Reserve will have to raise its main interest rate at least once by the end of this year. Higher interest rates would keep a lid on inflation, but they would also threaten to slow economies and undercut prices for stocks and all kinds of other investments.

The average long-term U.S. mortgage rate has already recently climbed to its highest level in nine months, and high costs to borrow money could discourage the building of AI data centers that are fueling the U.S. economy’s growth.

On Wall Street, J.M. Smucker jumped 11.2% after reporting a stronger profit for the latest quarter than analysts expected.

The company behind the Folgers, Hostess and other brands benefited from higher prices charged for coffee and sweet baked goods. It joined the long list of U.S. companies delivering stronger profit growth than analysts expected, which has helped drive the S&P 500 to record after record this year.

Nuvalent soared 39.2% after GSK agreed to buy the biotech company for $10.6 billion. The shares of U.K.-based GSK that trade in New York added 0.9%.

In stock markets abroad, indexes dipped in Europe following bigger moves in Asia.

South Korea’s Kospi jumped 8.2% and nearly recovered Monday’s plunge of 8.3%. It’s been beholden to the performance of big tech stocks like SK Hynix and Samsung Electronics.

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AP Business Writers Matt Ott and Elaine Kurtenbach contributed to this report