The mills, located in Youxian County in Hunan province, have been told to suspend operations while samples of rice stored at the mills is tested by the provincial quality inspection agency, Xinhua reported.
A May 16 statement by the Guangzhou Food and Drug Administration said eight of 18 batches of rice and rice products contained excessive amounts of cadmium.
Rice and rice products contaminated by cadmium have been found in two university cafeterias and two restaurants, the agency said.
Experts say they believe soil in some rice-producing areas could be contaminated with heavy metals such as cadmium. The heavy metals leach out of the soil and into the water, causing industrial water pollution.
All the tainted rice has been collected from local farmers, authorities said. All the closed mills were operating legally.