Entry and exit quarantine authorities in Shenzhen recently rejected a cargo of US corn because it contained genetically modified ingredients, a spokesman for the country’s top quality watchdog confirmed on Friday.

The cargo of corn, estimated to be more than 6 metric tons, was found by quarantine officers earlier this month to have contained MIR 162, a genetically modified ingredient that has not been approved for import by agricultural authorities, said Chen Xitong, spokesman for the General Administration of Quality Supervision, Inspection and Quarantine.

According to a regulation on genetically modified products issued by the State Council in 2001, only GM products that have been on the market and proven to be free of hazards to human and the environment can be imported to China.

Chen said the authority has notified US authorities and required its US counterparts to strengthen the quarantine of products before importing them.