Two South Korean exporters of enoki mushrooms were found to have been selling listeria-contaminated products. 

The Ministry of Agriculture, Food, and Rural Affairs and the Ministry of Food and Drug Safety on Wednesday announced the result of a joint investigation into four local companies that export mushrooms to the United States.

The inspection was launched after U.S. media reported that four deaths in the last four years, including two miscarriages, were linked to South Korean enoki mushrooms. 

The ministries explained that there have been no domestic food poisoning cases triggered by listeria-contaminated enoki mushrooms, and attributed it to the local custom of heating and cooking them before they are consumed. 

They said, however, the situation could be different in the U.S. as many Americans eat mushrooms raw in salads. 

The government plans to strengthen sanitary supervision of related products and order sellers to insert warnings labels on packages that inform consumers the product should be cooked before eating.