The Shing Mun River tributary in Fo Tan turned blue on Sunday. The case comes after a large quantity of dead fish washed up on the banks of a tributary near Tai Wai earlier in December.

Since the site of the latest pollution is near the Fo Tan industrial zone, some residents suspected that it was caused by illegal discharge of industrial waste, Apple Daily reported.

Tributary of Shing Mun River near Fo Tan. Photo: Apple Daily.

The site of pollution is a Shing Mun River tributary near the Fo Tan MTR station. The tributary water flows into the main river just upstream from the Hong Kong, China Rowing Association’s centre.

A student, surnamed Chan, told Apple Daily that the river stank. “Sometimes the river is in weird colours – purple, green,” she said. “[There are] black blocks floating in the river.”

Sha Tin District Councillor Scarlett Pong Oi-lan said that she had seen new dead fishes during her recent inspection of the river on Sunday. Although the government explained that heaps of dead fishes were washed ashore because many saltwater fishes could not survive in fresh water, Pong cast doubts on this explanation. She said she was concerned by the accumulation of sludge on the river bed, as it may cause the water quality to deteriorate.

Dead fishes on the banks of Shing Mun River. File photo: Apple Daily.

Cheng Luk-ki, Green Power’s head of scientific research and conservation, said the blue water could be caused by the dumping of pigment or die into river or rainwater drainage. He said these pollutants might be toxic.

He added that if the government wanted to develop sports and recreation activities on the Shing Mun River, then it should work on improving the water quality.

Cheng Luk-ki, Green Power’s head of scientific research and conservation. File photo: Apple Daily.

An Assistant Professor of the Department of Science and Environmental Studies at the Hong Kong Institute of Education, Tsang Yiu-fai, said that factories which might cause pollution were almost non-existent in Fo Tan, since the district had transformed from an industrial to a commercial area, reported Oriental Daily. Cheng said that the colour change might be caused by pigment powder from construction sites near Fo Tan station and the Hong Kong Sports Institute.

A spokesperson of the Environmental Protection Department said they had taken water samples from the river for tests while the Drainage Services Department said they had sent officers for an investigation on Sunday, but was unable to determine the cause of the colour change yet.

In early December, research by Greenpeace found that five biggest drinking water reservoirs in Hong Kong contain carcinogenic chemicals. The report also suggested that the Dongjiang River in China may be a source.