China has barred pork imports from six U.S processing plants and six cold storage facilities effective on Wednesday to enforce its ban on the use of a feed additive that promotes lean muscle growth, the U.S. Department of Agriculture said on Tuesday.

Reuters reports that China currently requires third party verification that U.S. pork shipped to the country is free of the additive ractopamine, which is sold for hog farm use under the name Paylean.

The facilities that are affected include Tyson Foods plants in Perry and Storm Lake, Iowa, and Logansport, Ind.; a Hormel Foods plant in Fremont, Neb.; a Triumph Foods plant in St. Joseph, Mo.; and a Quality Pork Processors plant in Austin, Minn.

Source: Reuters via CNBC