Water in the Cai Lon River in Hau Giang Province, southern Vietnam, has turned blackish in recent days. Photo by VnExpress/Thuan An

Local residents blame the pollution, which also causes the water to stink badly, on a nearby sugar factory discharging untreated effluents into the river.

Hau Giang authorities say they have taken test samples of the water to find the cause and take remedial action.

"This situation has been happening for 10 days now and is getting worse. Nearly all of the frogs, fish and shrimp farmed by some households have died and we have run out of clean water," said 35-year-old Pham Thi Thuy Linh, a resident of Long My Town.

The local water treatment plant has mobilized tankers to supply water to residents of Long My Town. Photo by VnExpress/Thuan An

Cai Lon River is the main source of water for Long My Town, whose water treatment plant uses around 4,000 cubic meters of water from the river per day to serve 6,000 families in the area.

But with the water so heavily polluted, the plant has had to turn to groundwater exploitation.

Nguyen Ba Nam, a local official, said: "The amount of groundwater collected is only about 1,200 cubic meters per day, so we have to mobilize tankers to transport water from the water plant in Vi Thanh Town (about 30 kilometers away)."

The Cai Lon River is about 60 kilometers long, originating in Long My District in Hau Giang Province and flowing northwest through several districts before merging with the Rach Gia Bay in Kien Giang Province.