Fox Business Network anchor Maria Bartiromo told "Bill Hemmer Reports" Wednesday that the coronavirus outbreak is causing the U.S. stock market to plummet due to American companies' dependence on China to preserve their supply chains.

Bartiromo explained that Chinese materials and components are used to make many products.

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"With the situation taking place here, you have bottlenecks of the supply chain," Bartiromo said. "You have companies that have products that they are trying to sell. Many of those components of those products -- whether it's cars, your phone, your washing machine, those components and parts are being made in China."

"There is no activity going in and out of China," Bartiromo added. "The planes have stopped -- No airlines, no activity there in terms of economic activity. That means no growth for China. And given the fact that China is such a bigger portion of the global economy today, that's going to impact earnings."

On Monday and Tuesday, the S&P 500 lost an estimated $1.7 trillion in market value as the spread of the virus around the world became apparent.

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Bartiromo noted that while the stock market has been on an upward tear during the Trump administration, any small variation could push the market down by a larger margin than usual.

"Having said that, this is a serious issue," she said. "This is a serious unknown. We don't know how far this goes. We don't know the duration of this coronavirus.

"Investors will sell first and think later. I don't think this is over just yet," Bartiromo added.

Observers have noted that even if a product is marked as "Made in USA," that product may still contain parts that were originally manufactured in China unless it consists of purely American materials.