U.S. markets were mixed early Tuesday as technology stocks gave back a chunk of their gains from a day earlier.

Futures for the S&P 500 lost 0.2% while futures for the Dow Jones Industrial Average ticked up 0.3%. Nasdaq futures fell 1%.

Semiconductor and memory-related tech stocks, which lifted markets on Monday, were broadly lower in premarket trading Tuesday.

In Asia, chipmaker Samsung Electronics slumped 7.7% despite a 19-fold surge in operating income surged in the last quarter. Its revenue more than doubled.

Artificial intelligence stocks have gyrated on fears of a bubble, raising questions about whether all the dollars flowing into AI chips and data centers can possibly create enough gains in productivity and profits to offset all the investments.

“The first proper AI stress test may not have arrived with weak demand, a capex warning, or some sudden crack in the data center story. It may have arrived with Samsung posting an extraordinary quarter and the stock falling anyway,” Stephen Innes of SPI Asset Management said in a commentary.

U.S. chipmaker Broadcom, which helped to pull markets higher on Monday with a 3.7% gain, gave most of that back overnight, sliding 2.8% before the opening bell. Micron, Marvell Technology and Intel were all down between 4% and 6% in the early going.

Western Digital, a data storage company whose stock has tripled this year on the AI wave, fell 7% before the opening bell.

SpaceX, which owns xAI, fell less than 1% ahead of its debut on the Nasdaq 100 index. That inclusion will force funds like the QQQ exchange-traded fund, which mimic the index, to buy SpaceX shares themselves.

At midday in Europe, Germany’s DAX shed 0.6%, the CAC 40 in Paris climbed 0.3% as did Britain’s FTSE 100.

Asian shares markets retreated, with South Korea’s Kospi closing 4.9% lower at 7,656.31 after dropping as much as 8% earlier in the day.

Tokyo’s Nikkei 225 declined 2.1% to 68,256.96. Computer chipmaker Tokyo Electron lost 3.9% and chipmaker Kioxia Holdings shed 11.3%.

The Hang Seng in Hong Kong declined 0.5% to 23,496.98, while the Shanghai Composite index gave up 1.3% to 3,990.24. Taiwan’s Taiex lost 2.3%.

In Australia, the S&P/ASX 200 declined 0.3% to 8,803.90 and India’s Sensex shed 0.1%.

In oil markets, the price of a barrel of Brent crude, the international standard, rose 69 cents to $72.68 a barrel. That’s close to where it was before the United States and Israel attacked Iran in late February, sending prices spiking.

The stability of supplies remains uncertain. A tanker traveling off the coast of Oman in the Strait of Hormuz caught on fire early Tuesday morning after being struck by a projectile, the British military said.

The attack was the latest targeting a vessel moving through the narrow mouth of the Persian Gulf, through which a fifth of all oil and natural gas traded once passed in peacetime. Iranian state television said the liquefied natural gas tanker came under attack after ignoring warnings but did not directly claim the assault.

U.S. benchmark crude added 56 cents to $69.11 a barrel.