BEIJING (AP) a¿¿ More than 8 million acres of China's farmland is too polluted with heavy metals and other chemicals to use for growing food, a Cabinet official said Monday, highlighting a problem that is causing growing public concern. The threat from pollution to China's food supply has been overshadowed by public alarm at smog and water contamination but is gaining attention following scandals over tainted rice and other crops. The government triggered complaints in February when it refused to release results of a nationwide survey of soil pollution, declaring them a state secret. The figure given at a news conference by Wang Shiyuan, a deputy minister of the Ministry of Land and Resources, would be about 2 percent of China's 337 million acres of arable land. Some scientists have given higher estimates of as much as 60 million acres, or one-fifth of the total, though it is unclear how much of that would be too badly contaminated for farming. The issue poses a dilemma for communist leaders who want to maximize food production but face public pressure to ensure safety after an avalanche of scandals over shoddy infant formula and other goods. The explosive growth of Chinese industry, overuse of farm chemicals and lax environmental enforcement have left swathes of the countryside tainted by lead, cadmium, pesticides and other toxins. Investigations by the Ministry of Environmental Protection have found "moderate to severe pollution" on 3.3 million hectares (8.3 million acres), Wang said at a news conference. "These areas cannot continue farming," Wang said. He did not say whether the information came from the national pollution survey. Farmers already are prohibited from raising crops for human consumption in areas across China that are deemed too badly polluted. But tainted rice and other crops have made their way into the food supply.