Toxic chemicals continue to threaten the safety of drinking water in the downstream regions of the Xiangjiang River, said local environmental officials.

After nearly a week of clean-up efforts, data still shows a level of cadmium still over the safety standards in certain areas, said Qu Lili, deputy head of environmental bureau in the downstream city of Xiangtan.

But Qu ruled out the media report that claimed cadmium levels of tap water in the city had surpassed the national safety standard two days after the spill.

"It's true that our water resources have been polluted, but our tap water has remained clean due to emergency chemical treatment," Qu said.

Cadmium, an industrial chemical that can cause neurological disorders and cancer, flooded into the Xiangjiang River during an unofficial silt-cleaning project started on January 4.