US meat processor Tyson Foods has seen half its pig slaughterhouses banned from exporting to China.

The United States Department of Agriculture announced that China was banning future pork imports from six US processing plants and six cold storage facilities over the use of a feed additive called ractopamine. According to the Department, China requires third-party verification that US pork imports are ractopamine-free.

The company has not made an official statement on the situation, or the effect it will have on the company. US pork exports to China in 2013 were worth in the region of US$645 million.

It comes just weeks after Russia banned food from the US as well as Europe in light of EU sanctions on Russia.

Tyson Foods processes 391,000 pigs per week and employs over 110,000 people. The company has nine dedicated pork processing plants, and pork products accounts for 13% of its international sales. It is responsible for 17% of the US pork processing trade.

Meanwhile, Russia has given the go-ahead to China to export pig products after its ban on imports from the US, Canada, Europe and Australia affects its pork supply. It has also approved more Brazilian plants to export pork to Russia.