LIUZHOU, Guangxi/BEIJING - The source of cadmium contamination in the Liujiang River had been blocked and tap water in Liuzhou is safe to drink, said environmental officials of the Guangxi Zhuang autonomous region on Wednesday.

Tap water from Liuzhou's four water plants was safe for drinking, Feng Zhennian, deputy director of the region's environmental protection bureau, told a news conference.

Polluted water detected in mid-January in the Longjiang River had flowed later into the Liujiang River, the water source for more than a million residents in Liuzhou.

Zhang Xiaojian, an expert with the river pollution task force, said on Wednesday: "The filtered cadmium will sink to the bottom of the riverbed. We will set up monitoring system and assess the environmental damage."

Cadmium is used in the manufacture of batteries, industrial paints and electroplating. Overexposure can damage the respiratory tract, liver and kidneys and can be fatal.

But Xiao Wenlian, director of the occupational health department of the Liuzhou disease control and prevention center, said the cadmium-tainted water would not cause direct damage to people's health immediately.

"Even if people drank seven liters of the water with a cadmium level twice the safety limit every day, only after 50 years of drinking it would cause kidney damage," Xiao said, adding there had been no reports of cadmium poisoning or tests for it in Liuzhou's hospitals.

Monitors at the Liuzhou disease prevention and control center examine water samples from various parts of the city on Wednesday. The monitors take samples every few hours to ensure tap water supply to city residents. Lan Lin / for China Daily