Stocks skidded after the Trump administration said it is imposing tariffs on steel and aluminum imported from Europe, Canada and Mexico, the AP reports. Canada and Mexico responded with tariffs of their own Thursday, and the European Union is expected to follow suit. American steel makers mostly rose, while industrial companies like Boeing and Caterpillar fell as they face the prospect of paying more for metals. US Steel added 1.7%, while Boeing lost 1.7% and Caterpillar fell 2.3%. The S&P 500 index lost 18 points, or 0.7%, to 2,705. The Dow Jones industrial average fell 251 points, or 1%, to 24,415. The Nasdaq composite gave up 20 points, or 0.3%, to 7,442. (More stock market stories.)