Stocks are turning sharply lower in afternoon trading as talk of steep tariffs on steel and aluminum spook investors.

The Dow Jones industrial average dropped as much as 500 points Thursday.

Industrial companies that would take a hit from higher steel and aluminum prices fell sharply.

Heavy equipment maker Caterpillar fell 2 percent and aerospace giant Boeing gave back 4 percent.

Big exporters like Apple and drugmaker Pfizer, which would suffer if trade tensions picked up, also fell.

The Standard & Poor’s 500 index dropped 41 points, or 1.5 percent, to 2,671. The benchmark index is coming off its worst month in two years.

The Dow was down 470 points, or 19 percent, at 24,554. The Nasdaq composite fell 127 points, or 1.8 percent, to 7,142.

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