The Chifeng city government in the Inner Mongolia autonomous region is stepping up investigations into tainted drinking water that made at least 2,622 residents ill and hospitalized 59 others, a senior official said Wednesday.

Inspectors are looking into reports of a delay in alerting residents of the polluted water supply, as well as investigating any other cause of the contamination other than the heavy rainfall, Gao Xihua, secretary-general of the local government, told China Daily.

"Discharge from septic tanks or chemical factories are possible causes in this case, but investigations are ongoing," Gao said, adding that the diarrhea-causing bacteria colon bacillus is one of the main contaminants of the water.

The latest investigations have found that the pollution was partly due to a power cut at a sewage pump station, about 150 m west of the polluted reservoir in the new downtown area. This led to the discharge of raw sewage into the reservoir, Gao said.

Generally, reservoirs supplying tap water are built at least one meter above the ground and no chemical factories are permitted within a 500 m radius, according to typical standards, like those for the Beijing waterworks.

The heavy rain in Chifeng last Thursday had raised water levels in the affected area to about half a meter, Gao said.

But the notices not to drink the tap water were not delivered until Sunday. Officials from the Chifeng commission of housing and urban-rural development delivered more than 20,000 notices before 8 pm that day.

Seven fire trucks have been delivering clean water to 18 communities in the new downtown area every day since Tuesday.

Local authorities have also beefed up support to sickened residents since Sunday, he said.

Similarly, local health authorities have required eight hospitals to expedite treatment for patients sickened by drinking the contaminated water.

Most of those who were sickened by the tainted water suffered from fever, diarrhea, nausea or vomiting.

The city's population is 4.5 million with 58,000 living in the new downtown, Xinhua reported yesterday.

Many experts do not think heavy rain is the sole reason for the pollution. Li Shanzheng, professor from the Beijing Hydraulic Research Institute, said that with proper protection measures, it is unlikely that rain and other dirty water can infiltrate the reservoir water.

"Reservoirs are required to be located at least one meter higher than ground level. Except for outright floods, it is impossible for heavy rains to overflow into the reservoirs," a worker from Beijing waterworks group, who refused to be named, told China Daily yesterday.

"If the government had responded in a more timely fashion and stopped the water supply, fewer people would have gotten sick," Li said.

Many netizens also condemned the notice delay. A netizen called lg12345007 posted on the major online forum Tianya that covering up a water pollution problem is worse than the water pollution itself.

(China Daily July 30, 2009)