BEIJING — China has asked pork processors and hog dealers to secure certificates proving their products are free of African swine fever.

The order, contained in a central government circular, took effect on May 1.

Processors and dealers should have all pork products examined for the swine fever virus, said the circular jointly issued by the State Administration for Market Regulation, the Ministry of Agriculture and Rural Affairs and the Ministry of Industry and Information Technology.

More inspections to farmers’ markets, traders and restaurants are also ordered. Violators will face harsh punishment, the circular said.