State media in China say authorities have stopped a toxic chemical slick from reaching the major southern metropolis of Guangzhou by closing a dam on the Bei River.

The China Daily newspaper reports Friday that government workers have lowered the gates of the Baishiyao dam to trap the cadmium spill. The dam is about 100 kilometers north of Guangzhou, a densely populated city of about 10 million people. A local government spokesman says the water quality south of the dam is safe.

Farther upstream, officials plan to dilute the cadmium by releasing nearly 400 billion liters of water from a reservoir into the Bei River.

The contamination of the river by a smelter in Guangdong province a week ago is China's second major environmental incident in recent weeks.

Some information for this report provided by AFP and Reuters.