Investor jitters over the economic fallout of Britain’s vote to leave the European Union sent U.S. stocks sharply lower Monday.

The Dow Jones industrial average lost 260.51 points, or 1.5 percent, to 17,140.24. The average had been down more than 337 points earlier in the day.

The latest slump followed another rough day for European markets and a further weakening of the euro and British pound, which plunged to its lowest level since 1985.

Ratings agency Standard & Poor’s added to the market’s anxiety Monday by stripping the UK of its top-shelf credit rating. The firm cited uncertainty over the UK’s vote to leave the EU.

Materials companies led the slide on Wall Street. Losses also piled up for financial and technology stocks. Shares in energy companies fell as the price of U.S. crude oil declined.

Utilities stocks, traditionally seen as a more attractive investment at times of heightened market volatility, rose.

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“When you get major news like this that is unexpected, as the ‘Brexit’ vote was, it often takes about five trading days to kind of work through the system,” said JJ Kinahan, chief strategist at TD Ameritrade.

The S&P 500 index slid 36.87 points, or 1.8 percent, to 2,000.54. The Nasdaq composite fell 113.54 points, or 2.4 percent, to 4,594.44.

The Dow, S&P and Nasdaq indexes are down for the year.

Britons voted last Thursday to leave the EU over concerns including immigration and regulation. That move created a wave of uncertainty for financial markets, triggering a sell-off on Friday that resulted in the biggest losses for the Dow and S&P 500 since August, while the Nasdaq notched its worst day since August 2011.

Despite the losses on Friday and Monday, the market is still well above the lows it reached in early February, when the S&P 500 closed as low as 1,829.