Companies importing pork from the United States must provide test reports indicating that there are no traces of ractopamine in the meat before it can enter the Chinese market starting from March 1, China's top quality control authority said on Thursday.

Ractopamine, a feed additive used to promote lean muscle growth, is banned in China.

The regulation is to protect the health of Chinese consumers after traces of the substance were detected in pork imported from the US on multiple occasions, according to the General Administration of Quality Supervision, Inspection and Quarantine.

The total value of US pork exports to the Chinese mainland and Hong Kong last year was $886 million, according to media reports.