The Guangdong Province cities of Guangzhou and Foshan were ordered yesterday to start emergency plans to provide safe drinking water to residents as a toxic slick of cadmium approaches in the Beijiang River.

Local governments along the river have set up 20 monitoring stations to test the water quality.

Environmental protection experts said cadmium levels dropped after water was discharged from reservoirs into the upper reaches of the Beijiang River.

They said the polluted water will likely not threaten the drinking water source for residents in Foshan and Guangzhou, the provincial capital. Nevertheless, the two cities have been asked to plan for a possible emergency.

Zhang Lijun, deputy director of the State Environmental Protection Administration, arrived in Yingde with 14 experts on Tuesday.

The slick arrived in Yingde on Tuesday.

As of 11pm that day, the water supply was "still safe" in Yingde, said an official with the municipal government who declined to give his name.

Residents to the north near Baishiyao Hydropower Plant, however, were warned not to drink the tap water, according to a government television notice broadcast on Tuesday evening.

Yingde has begun to build a 1.4-kilometer pipeline that connects to a reservoir pipeline. Once built the city will receive fresh water directly from the reservoir.

"The water pipe will be built within 36 hours before the toxic slick arrives in the urban district," said a Yingde government official.

In addition, a large quantity of water carriers, including 15 fire engines, have been commissioned to send drinking water to the city.

According to environment officials, the cadmium slick was caused by excessive waste discharges from a smeltery in Shaoguan City, about 90 kilometers north of Yingde.

The state-owned smeltery halted operation and closed the waste water outlet blamed for the excessive discharge, according to Shaoguan's environmental protection office.