BEIJING, Nov. 29 -- Chinese authorities discovered 1,659 batches of substandard food imports in the first nine months of this year, the country's top quality supervisor announced on Friday.

Wrong labels, microbial contamination and poor quality were the main problems discovered in these food imports, according to the General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ).

The rejected food products fall into 21 categories, with most of them classified as dairy products, alcohol, cake and biscuits, beverages and grain products, said AQSIQ spokesman Chen Xitong.

All substandard products were either sent back or destroyed, Chen said.