At least 10,000 people in a south China town suffered a shortage of drinking water Wednesday after excessive manganese was detected in the tap water.

The city government of Lufeng in Guangdong Province said the manganese level in the tap water in Da'an town was 1.2 mg per liter since Monday, 12 times the maximum amount allowed in drinking water.

The cause of the contamination was still under investigation and environment specialists from Lufeng City were in town to conduct further analysis, said Huang Xianjia, a city government spokesman.

According to the safety standards for drinking water, jointly issued by the Ministry of Health and the Standardization Administration in 2007, the maximum manganese level allowed is 0.1 mg in every liter of drinking water.

The local government put up emergency notices on every busy street in town Tuesday, warning residents not to drink tap water until further notice.

"We're trying to remedy the situation and will keep you posted," reads a notice written on scarlet paper.

Huang said the contamination was "not serious." "Tap water still appears clear with no odor. It's safe for washing and bathing."

But a resident surnamed Wang showed reporters two pails of water he stored on Monday. Dark sediment was seen clearly on the bottom of the pails.

"It takes time for the mineral to settle and become visible," said Wang.

Wang and his neighbors have joined a rush for spring water in mountains near their homes. "Many families have bought new pails. Some carry water on motorbikes while others use shoulder poles," he said.

Da'an town has several spring water resources nearby so drinking water is not an immediate worry, said Huang Zhenyu, chief of the local government.

He said police and market regulators had been told to watch out for price hikes as shopping sprees for bottled water and food were likely.

The manganese-tainted water comes from Da'an Waterworks, one of the two tap water suppliers in town. It provides water for more than 10,000 of the town's total 50,000 residents.

It was the first manganese contamination case reported since the waterworks became operational in the 1980s.

The cause of the contamination is still unknown. Town official Huang Zhenyu said there was no manganese processing plant or mine around.

He said lab tests were being done at the other waterworks. "If the water there proves safe, we'll lay a new pipeline to divert some of its water."

Health experts say manganese is a required nutrient, but high levels of the mineral can pose a neurotoxic risk, causing mental and emotional disturbances and difficulty in moving.