Police in the northern province of Hoa Binh said on Friday they had made urgent arrests of two men suspected of dumping waste oil into a local stream, contaminating a major source of Hanoi’s tap water and leaving millions out of clean water for over a week.

The suspects are Nguyen Chuong Dai and Hoang Van Tham, who work as for-hire truck drivers, a leader of Hoa Binh Police told Tuoi Tre (Youth) newspaper on the same day.

On October 6, Chuong and Tham were hired by a man called Ly Dinh Vu to dispose of waste matter from a ceramic tiles factory in the northern province of Phu Tho, according to what they told the police.

Around ten cubic meters of waste matter from the tiles factory was fed into ten empty tanks on a truck, which they drove to Hung Yen Province and parked there overnight.

On the night of October 8, Chuong and Tham drove the truck while Vu drove a car to Ky Son District in Hoa Binh Province, about 60 kilometers west of Hanoi, where they dumped the waste matter into a local stream.

Due to a downpour later that night, the oil quickly spread to a nearby canal, which led water from the Da (Black) River into a water treatment plant of the Song Da Water Investment JSC (Viwasupco).

The contamination caused the tap water in a large area in Hanoi to reek of a strong smell - later identified as that of styrene - for days this week and the last.

Waste matter flows into the Da (Black) River in Hoa Binh Province from a nearby stream, turning the river water into a blackish color. Photo: Le Hoang / Tuoi Tre

Viwasupco, which supplies water to several districts in the western part of Hanoi, cut its water supply on Tuesday and Wednesdayto cleanse its pipelines, causing severe water shortage in the districts of Hoai Duc, Hoang Mai, Thanh Xuan, and Nam Tu Liem.

Residents were seen making long lines at night and under the rain for clean water from tanker trucks earlier this week, while demands for bottled water also skyrocketed due to the water scarcity.

Unofficial numbers show that around 1.4 million people in the Vietnamese capital city were affected by the water contamination.

Residents in Hanoi queue for clean water from a tanker truck. Photo: Quang The / Tuoi Tre

Hoa Binh Police said they are still hunting for Vu - the third suspect in the case, after having confiscated the car that he drove to the dump site on October 8.

Residents are encouraged to report any sighting of the man to the local police or try to keep the suspect contained until law enforcement arrives, should conditions allow.

A criminal investigation was launched into the case on Thursday.

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