China's deep underground drinking water sources are safe, an official at the Ministry of Water Resources said on Monday in response to a news report suggesting that more than 80 percent of the water in China's aquifers is too polluted for human consumption.

The official, Chen Mingzhong, said monitoring does not show that underground sources of drinking water are threatened, since most of the country's water for human consumption is extracted from deep underground, not near the surface.

Monitoring by the ministry shows that 85 percent of the 1,817 groundwater sources used to extract drinking water meets quality standards, and the 33 sources that supply drinking water to cities with a population larger than 500,000 all meet water quality standards, Chen said.

Ma Jun, director of the Institute of Public and Environmental Affairs, a non-governmental environmental protection organization, said most cities in China are using water from deep underground - which is not easily contaminated - for drinking.

"However, many people in rural areas are still drinking shallow groundwater. Contamination could affect them," he said.

Incidents of water contamination have increased over the past several years, with more than 1,700 reported annually. At least 140 million urban people have been affected.

According to the report released by the ministry last week, groundwater quality is far from satisfying. Water in one-third of the non-drinking-water wells monitored was classified as Type IV, which is suitable only for industrial or entertainment purposes.

Water in 47 percent of the wells was listed as Type V, referring to more polluted water suitable only for agriculture or landscaping.

The ministry's report captured public attention after National Business Daily said more than 80 percent of China's groundwater is threatened by pollution.

The ministry's finding was based on its monitoring of water in more than 2,100 wells - none of them used for drinking water - in various places in China. The effort began last year. Areas monitored included the Songliao Plain in the northeast, Huang-huai-hai Plain in the north, Jianghan Plain in Central China and basins and plains in the west.

Data from the Ministry of Land and Resources show that among 657 Chinese cities, more than 400 were using groundwater for drinking. More than 70 percent of people nationwide drink groundwater.