About 20 minutes into trading, the Dow Jones Industrial Average was down about 500 points, or 1.9%, at 25,983.81.

The broad-based S&P 500 fell 2.0% to 2,874.83, while the tech-rich Nasdaq Composite Index slumped 2.5% to 7,801.37.

China’s currency tumbled below 7.0 against the dollar, which investors see as a key threshold in currency value, only days after President Donald Trump announced plans to impose tariffs on US$300 billion in additional Chinese imports.

Trump’s tariff announcement sparked a selloff that led to the S&P 500’s worst week so far in 2019.

In a statement on Monday morning, the People’s Bank of China said the exchange rate against the US dollar had been “affected by unilateralism and trade protectionism measures and the imposition of tariff increases on China.”

Losses were broad-based but included several companies with significant China businesses, including Apple, which shed 4.1%, Boeing and General Motors, both of which lost 2.3% and Caterpillar, which shed 2.0%.