Stocks fell on Thursday after President Donald Trump slapped tariffs on the European Union, Mexico and Canada, sparking fears the U.S. could enter a trade war with some key partners.

The Dow Jones industrial average dropped 251.94 points to close at 24,415.84, with Boeing contributing the most losses to the index. The declined 0.7 percent to 2,705.27 as consumer staples lagged. The Nasdaq composite, meanwhile, pulled back 0.3 percent to 7,442.12.

The Trump administration said tariffs on steel and aluminum imports from EU, Canada and Mexico will take effect at midnight Thursday. The EU followed up the U.S. announcement by saying it would impose countermeasures of its own, while Canada Foreign Minister Chrystia Freeland said the country plans to slap dollar-for-dollar tariffs on the U.S.

Mexico responded to the measures by saying it would impose tariffs on apples, pork bellies, and flat steel imported from the U.S.

Metal producers in the countries affected had been granted a temporary exemption from the tariffs earlier this year, but they are set to expire Friday. The tariffs were originally announced on March 1.