More than 10,000 tons of cadmium-tainted rice are believed to have entered Guangdong province markets since 2009 from suppliers in Hunan province, Nanfang Daily reported on Wednesday.

Shenzhen Cereals Group, a State-owned enterprise for grain reserves and a major rice supplier in Guangdong, bought the rice in 2009 from branches of China Grain Reserves Corp in Hunan province, the report said.

Samples of the rice that Shenzhen Cereals subsequently sent to food quality supervision authorities in Shenzhen showed that the rice had excessive cadmium.

The company complained and had a supplier in Xiangtan, Hunan province, recall 180 tons of the tainted rice. But the recalled rice was resold to a mill that produces rice flour in Foshan, Guangdong province, the report said.

Shenzhen Cereals accepted the bulk of cadmium-contaminated rice on the condition that its price be cut, and the company later sold the rice at a higher price to clients that included a rice flour mills in Dongguan, a brewery in Guangzhou, and retailers in Shenzhen, the report said.

Shenzhen Cereals allegedly knew about cadmium contamination in rice as early as several years ago, when it started business with suppliers in Hunan.

The company did not complain and in fact continued to buy in large quantities until the rice market took a downturn in 2009, according to the report.

Shenzhen Cereals had already made large purchases before the price drop. It tried to negotiate with suppliers in Hunan province for a lower price, but after the company was rebuffed, it used the unfavorable cadmium testing results to force suppliers to cut their prices, the report said, citing several managers of grain reserves offices in Hunan province.

Angered by the move, suppliers in Hunan cut all business ties with Shenzhen Cereals.

In the past few years, Shenzhen Cereals sent purchase managers to Changsha with orders and promises of big profits. The requests were all turned down, the report said, citing Chen Jian, a manager at the grain reserves office in Changsha.

Chen said rice tainted with cadmium is a widespread problem in Hunan because of tainted soil, water and air.

Despite the excessive cadmium levels, rice in Hunan is still in high demand.

The report revealed that testing the quality of rice was poorly enforced in Hunan. The typical procedure does not test for residues of pesticides or cadmium levels, which makes the tests easy to pass. And only a small percentage of products are sampled, which leaves a large amount of rice unexamined.

Medical experts have warned that continual exposure of cadmium over a long time may lead to cancer. Crops grown in polluted soil may have higher cadmium concentration and produce tainted rice.

Human exposure to the heavy metal can cause severe health risks that include kidney and respiratory problems.