Market traders and restaurants in Northeast China have seen sales slump after a meatpacking factory was found using cheap duck meat and additives to replicate mutton and beef slices.

Police seized more than 50 metric tons of products at Shengtai Meat Processing Plant in Liaoning province's Liaoyang county, the Ministry of Public Security said on Sunday.

The products were made from duck meat steeped in mutton fat and other additives, in order to lower production costs, according to a statement posted on the ministry's website.