BEIJING, Dec. 20 -- China has rejected 12 batches of U.S. corn shipments tainted with a genetically-modified (GM) strain not approved by the country's agriculture ministry, its leading quality supervisor said on Friday.

Shipments totalling 545,000 tonnes were found to contain the unapproved MIR162, a strain of insect-resistent transgenic corn, the General Administration of Quality Supervision, Inspection and Quarantine said in a statement.

The administration said local entry-exit inspection and quarantine bureaus have returned the batches and it has notified the U.S. authority.

It urged the U.S. authority to improve its inspection procedures to ensure that they comply with Chinese quality standards.