The ministry said it will probe imports from January 2013 to October 2017 and while it aims to complete the inquiry by next February, it could potentially extend until August 2019.

Wang Hejun of China’s Investigation Bureau of the Ministry of Commerce said in a statement that there is preliminary evidence that the U.S. government has “provided subsidies to sorghum.”

“Since 2013, U.S. exports of sorghum to China have risen sharply and prices have continued to drop, damaging the sorghum industry in China,” he said. “To this end, the Ministry of Commerce decided to launch the investigation in accordance with the relevant laws of China and the WTO rules.”

The United States is the world’s top exporter of sorghum and China’s largest supplier by far, with imports from the United States reaching 4.76 million tonnes in 2017, out of just over 5 million tonnes in total.

China primarily uses sorghum to feed its large livestock sector.

The trade action comes a year after Beijing slapped hefty anti-dumping and anti-subsidy duties on imports of distillers dried grains (DDGS) from the United States, another product used as a feed ingredient.