Chinese safety regulators say rotten feed fed to cows caused the high levels of a cancer-causing toxin found in milk at two dairy companies, including the country's biggest. It is the troubled dairy industry's latest scandal.

A statement posted late Monday on the quarantine and safety administration's website said an expert review identified mildewed feed as the cause of the excessive levels of aflatoxin in milk from the two dairies.

The agency says it is ordering industry giant Mengniu Dairy Group and the Fujian Changfu Dairy Industry Group to destroy the tainted products. The agency says the contamination should stop once the cows stop eating the rotten feed.

Aflatoxin is produced by a fungus that commonly breeds on grains.