People in Tan Hai Commune of southeast Ba Ria-Vung Tau Province had 10 days prior discovered a detention basin located near several seafood processing factories had started releasing an unpleasant smell while the water had turned murky. By Thursday, the water had taken on an alien pink-purple color, with the pungent smell becoming unbearable.

The basin holds treated wastewater from factories, and acts to regulate flooding during the rainy season. When the floodgates are opened, the water would typically flow toward Rach Van and Cha Va rivers before reaching the sea, where hundreds of families cultivate seafood.

Vu Thanh Tinh, a local, said the incident has heavily impacted dozens of families in the area.

"With this color and stench, no creature could survive here," he said.

The cause of the color change has yet to be confirmed, but a survey by Ba Ria-Vung Tau authorities late last month revealed wastewater from Nghe Huynh Company, which processes fish powder, had entered the basin. The water stemmed from toilets, wastewater from hand washing, and manufacturing, typically blackish in color.

Test results showed the water did not meet environmental standards, so the company was requested to suspend production and prevent the wastewater from flowing into the basin.

Besides Nghe Huynh, authorities also found Dai Quang, which illegally processes cowfish, was still in operation despite the provincial People’s Committee having requested it to stop operating in the past.

The provincial Department of Natural Resources and the Environment said it is monitoring seafood processing facilities near the basin and working with experts to improve its water quality. The department also requested an immediate suspension of Dai Quang and other violating companies.

This was not the first time the basin’s water had changed color. A similar incident occurred in 2017, when authorities discovered algae blooming triggered by pollution.

In 2015, the province had spent billions of dong (VND1 billion = $43,500) to renovate the basin and moved some seafood processing factories away from the area after discovering wastewater from 14 facilities was discharged directly into the Cha Va River, killing tons of fish.