China's quarantine authorities rejected another 286,000 metric tons of US corn imports in January and February for contamination with the unapproved genetically modified MIR 162 strain, a spokesman for the country's quality watchdog said on Friday.

As of Feb 24, quarantine authorities in China had rejected 887,000 tons of US corn for containing the strain, which is yet to be approved by the country's agricultural authorities, Chen Xitong, spokesman for the General Administration of Quality Supervision, Inspection and Quarantine, said at a news conference.

All the rejected corn has been returned to the United States, Chen said.

The MIR 162 stain, developed by Swiss agri-business company Syngenta AG, was first detected by quarantine authorities in Shenzhen, Guangdong province, in November.