Environmental protection authorities in south China's Guangdong Province said on Saturday that no chromium pollution has been detected in a major river that flows through the province, responding to an online claim that the river's headwaters were polluted.

Water quality monitors have not seen any signs of chromium in the Pearl River, a water source for tens of millions of the province's residents, a senior official from the Guangdong Provincial Environmental Protection Department said.

Posts on weibo.com, a popular Chinese microblogging site, claimed that 300,000 cubic meters of chromium-polluted water were piped into the Nanpan River, located upstream from the Pearl River, spawning public concerns over water safety in the country's most populous region.

The posts cited a report from a local newspaper in southwest China's Yunnan Province, where the Nanpan River is located.

The report said that the government of the city of Qujing piped a large amount of polluted water into the Nanpan River from a nearby reservoir which has been polluted by 5,000 metric tons of chromium tailings near the reservoir.

Yunnan's environmental protection authorities issued a notice on Saturday, stating that the water quality of the Nanpan River had not been compromised.

Guangdong environmental protection authorities will closely monitor the river and update the public as necessary, the official said.