U.S. stock futures tumbled Thursday, with selling so intense at one point that circuit breakers were triggered, after the arrest of a Huawei executive reignited trade worries that helped drag equities to their worst session since early October on Tuesday.

The market was closed Wednesday to mark a national day of mourning for former President George H.W. Bush, who died Friday at 94.

How did the benchmarks fare?

Futures for the Dow Jones Industrial Average YMZ8, -1.83%  were down 448 points, or 1.8%, at 24,606, while those for the S&P 500 index ESZ8, -1.80%  were off 46.70 points to 2,655.75, a loss of 1.7%, while Nasdaq-100 futures NQZ8, -2.45%  tumbled 159 points, or 2.4%, at 6,642.50.

On Tuesday, the Dow DJIA, -3.10% sank 799.36 points, or 3.1%, to 25,027.07, while the S&P 500 index SPX, -3.24% dropped 90.31 points, or 3.2%, to 2,700.06. The Nasdaq Composite Index COMP, -3.80%  tumbled 283.09 points, or 3.8%, to 7,158.43. All three benchmarks had their worst day since Oct. 10.

Read: The worst-performing stocks on ‘Tariff Man’ Tuesday

What drove the market?

While regular trading was closed Wednesday, there was a shortened session of electronic trading for stock-index futures that showed Dow futures bouncing 100 points. When futures reopened Thursday, the drop was so severe on S&P 500 futures that the Chicago Mercantile Exchange triggered circuit breakers to avoid worse losses. Those futures spiked down to 2,659, a drop of 1.9% before the CME stopped trading briefly to try to calm the market, said Chris Weston, head of research at Pepperstone.

S&P 500 futures tumble sharply at Thursday’s reopen

Already jittery investors were rattled further by news that the Canadian authorities had arrested Meng Wanzhou, the chief financial officer of Huawei Technologies, at the request of U.S. authorities for allegedly violating sanctions against Iran. The arrest, which was made on Dec. 1, comes as the U.S. has taken several steps to restrict the Chinese technology giant, trying to persuade international allies to do the same.

China authorities reacted furiously, with the spokesperson of the Chinese Embassy in Canada demanding the release of the Huawei executive. “At the request of the U.S. side, the Canadian side arrested a Chinese citizen not violating any American or Canadian law,” said a statement on its website. Huawei itself said it was “unaware of any wrongdoing by Ms. Meng,” in a statement released on Twitter.

The latest development comes amid an already shaky backdrop for trade relations between the U.S. and China. Doubts surrounding the weekend trade moratorium at the G-20 summit between the two sides and ominous developments in the bond market drove sharp losses for stocks Tuesday.

Investors are also facing a heavy load of economic data Thursday and the start of a two-day OPEC meeting. That data batch includes ADP employment for November that will be released at 8:15 a.m. Eastern Time, followed by weekly jobless claims, the October trade deficit and third quarter productivity and unit labor costs, all at 8:30 a.m. Eastern.

The Institute for Supply Management’s nonmanufacturing index for November will be released at 10 a.m. Eastern, along with October factory orders and the quarterly services survey for the third quarter.

What are strategists saying?

“The timing of the arrest is key here. Markets are already incredibly nervous over slowing economic growth thanks to the inverted U.S. yield curve. Relations between the U.S. and China were supposed to be on the mend after a productive G-20. However, the arrest has the potential to shatter very fragile U.S.—Sino relations which will weigh further on global trade and growth concerns,” said Jasper Lawler, head of research at London Capital Group, in a note to clients.

And “despite recent heavy selloffs, the bottom isn’t in sight and the markets have further to fall. The big swings of late are representative of a very jittery market,” added Lawler.

Read: December historically is the most wonderful time of the year for stocks

What are other markets doing?

Asian stocks fell sharply across the board, with the bulk of losses hitting tech stocks, and the Hong Kong Hang Seng Index HSI, -2.47%  bearing the brunt of losses, dropping 2.5%. European stocks SXXP, -2.33%  also traded lower across the board.

Benchmark U.S. crude CLF9, -4.59%  lost nearly 3% to $51.35 a barrel. Brent crude LCOG9, -4.66% used to price international oils, declined close to 3% to $59.76, as traders awaited clarity on a possible, but far-from-assured, output cut by major producers gathering in Vienna.

OPEC will hold its official meeting on Thursday, with another key meeting between the group’s members and nonmember allies to be held Friday.

Gold prices GCG9, -0.06%  traded steady, along with the ICE Dollar Index DXY, +0.14%

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