By Jack Pitcher and Isabella Simonetti

A wild stock-market swing based on false information added $2.4 trillion in value and erased it almost as quickly Monday morning.

The episode played out in just over half an hour, all based on misleading reports that said President Trump was considering a 90-day pause to implementing tariffs.

The rally-turned-rout underscored how feverish many investors are for any information that might calm the market and how easily misinformation and Wall Street's high-frequency trading strategies that react to headlines in seconds can impact asset prices.

News that tariff-shocked investors had been dying to see began circulating on social media shortly after 10:10 a.m. in New York: "HASSETT: TRUMP IS CONSIDERING A 90-DAY PAUSE IN TARIFFS FOR ALL COUNTRIES EXCEPT CHINA," the headline read, in an apparent reference to words from Kevin Hassett, director of the National Economic Council.

Stock indexes soared. After trading as much as 4.7% lower early in the session, the S&P 500 rose to trade up 3.4% in a jarring intraday reversal. The broad-based index added $2.4 trillion in market value in the 10 minutes from 10:08 to 10:18 a.m., according to Dow Jones Market Data.

By 10:41 a.m. it had all been wiped out. The S&P 500 erased $2.5 trillion in value in around 23 minutes after the White House quickly denied that such a pause was being discussed.

After the false headline caused the S&P 500 to trade in its widest intraday range since March 2020, the index closed down just 0.2%.

The origin of the report remains unclear. The headline was circulating on social media by 10:13 a.m., when a widely followed X account known as Walter Bloomberg posted it.

The anonymous account has for years posted trading-related news throughout the market day, often in the form of all-caps newswire headlines copy-and-pasted from the Bloomberg Terminal. The account, which has nearly one million followers, isn't associated with Bloomberg News. The Walter Bloomberg account and others like it are popular with market watchers who don't have access to Bloomberg's expensive news-and-data terminals.

The headline in question didn't come from Bloomberg's newswires, however. And the news was quickly gaining steam with major outlets. A CNBC anchor read the news live on air around 10:15 a.m., before warning viewers that, "We'll try and source that, exactly where that came from."

At 10:20, Reuters sent the same news over its wires, attributing it to CNBC.

"As we were chasing the news of the market moves in real-time, we aired unconfirmed information in a banner. Our reporters quickly made a correction on air," a CNBC spokeswoman said.

A Reuters spokeswoman said: "Reuters, drawing from a headline on CNBC, published a story on April 7 saying White House economic adviser Kevin Hassett had said that President Trump was considering a 90-day tariff pause on all countries except China. The White House denied the report. Reuters has withdrawn the incorrect report and regrets its error."

The original headline might have been an inaccurate summary of an interview Hassett gave on Fox News earlier Monday morning. In a "Fox & Friends" interview before the market opened, Hassett was asked if the White House would consider a 90-day pause on the tariffs.

"Yeah, I think the president is going to decide what the president is going to decide. There are more than 50 countries in negotiation with the president," Hassett said, without elaborating further on a potential pause.

Write to Jack Pitcher at jack.pitcher@wsj.com and Isabella Simonetti at isabella.simonetti@wsj.com

(END) Dow Jones Newswires

April 07, 2025 16:34 ET (20:34 GMT)

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