New York CNN  —  US stocks tumbled Monday after fresh data stoked concerns about the economy’s health. The Dow slid 300 points, or 0.8%, after tumbling more than 400 points earlier in the day. The S&P 500 declined 0.3% and the Nasdaq Composite added 0.1%. That comes after the Institute for Supply Management manufacturing index clocked in at 48.7% in May, down from 49.2% in April. A reading below 50 indicates signs of contraction in the US manufacturing industry, while a reading above that level signals expansion. “Today could mark a significant turning point in equity markets. In recent months, investors have cheered weaker-than-estimated data based on expectations that it could accelerate the start of the Fed’s policy loosening. Investors are now reacting to soft data with fear,” wrote José Torres, senior economist at Interactive Brokers, in a Monday note. Shoppers carry shopping bags while walking through The Village at Corte Madera on May 30, 2024, in Corte Madera, California. Economists expected US consumer spending to grow at a slower pace in April than it did in March. Justin Sullivan/Getty Images Related article The Fed’s favorite inflation gauge showed little progress last month Investors have in recent weeks grappled with data that suggests inflation is continuing to run hot while the economy cools. That has spurned concerns that the Federal Reserve will keep interest rates higher for longer than expected, in turn sending stocks swinging. Still, all major stock indexes in May cinched their sixth winning month in seven. The Personal Consumption Expenditures price index, the Fed’s preferred inflation gauge, showed Friday that inflation stayed stubbornly high in March. PCE rose 0.3% on a monthly basis and 2.7% from the year prior, according to Commerce Department data. New gross domestic product data released last Thursday showed that the US economy expanded at a weaker pace earlier this year than initially reported. The Commerce Department’s second estimate of first-quarter gross domestic product registered at a 1.3% annualized rate, below the 1.6% reflected in the first estimate, largely due to a downward revision to consumer spending. “I don’t think we are going into a recession, but we are normalizing,” said Keith Lerner, chief market strategist at Truist. Elsewhere, the New York Stock Exchange said Monday that a technical issue that halted trading for some stocks and caused Berkshire Hathaway shares to be down 99.97% has been resolved. This is a developing story and will be updated. CNN’s Matt Egan contributed to this story.