China's market regulator said Friday that it has launched an antimonopoly probe into DuPont's China operations, the latest in a slew of retaliatory measures from Beijing following President Trump's imposition of tariffs. DuPont shares tumbled 8% in premarket trading.

The chemical and materials manufacturer relied on China and Hong Kong for 19% of its revenue last year, according to its latest annual report. It has manufacturing facilities in several Chinese cities and a research and development center in Shanghai.