Attracted by huge profits, many people are continuing to dredge up sand from the Dong Nai River in the south and the Hong (Red) River in the north as law-enforcement officials have found it difficult to prevent the illegal activity.

Along the Dong Nai River that traverses its namesake province and in HCM City, sand exploiters have become more and more aggressive as profits rise.

According to sand traders, a cubic metre of sand costs from VND80,000 to VND100,000 (US$4-5). A boat can absorb from 30 to 50cu.m of sand a night.

Boats used in sand exploitation use hoses with the diametre of the size of a human thigh to soak up sand from both banks of the river, as the riverbed has been over-exploited.

They work mainly overnight to avoid being caught by patrolling forces.

In District 9's Long Phuoc Ward, around 30 boats every night suck up hundreds of cubic metres of sand, causing losses of land, landslides or water flow changes.

"It's deadly to fight them because they all keep scimitars or axes in their boats," said Mai Van Luan, a fisherman working on the river.

"So I just keep silent as they work, even though it pains me to see that."

Sand exploiters take sand from pieces of riverside land owned by wealthy residents of HCM City who visits during the weekends.

"Once they stonned and threatened to cut my head when I begged them not to take sand," said Nguyen Van Thanh, who was hired to guard a piece of land.

He had to quit his job after just one month to ensure his own safety because he worked alone at night.

Some landowners have bought loads of cobblestones to cover and protect their sand from being taken, but the measure has not been effective.

Exploiters place sand bags at scattered consolidated sites along riverbanks where they trade with customers who are hungry for sand to use in construction. The sites are like outdoor sand markets.

Illegal sand appropriation thrived in the area 13 years ago and immediately slowed down when law-enforcement authorities of both HCM City and Dong Nai Province began to crack down on the practice.

However, three years later, sand thieves began attacking the river after the monitoring by police was relaxed.

"Every time we could only capture one or two boats, at most, because the others were quickly informed via mobilephones and ran away immediately," said Chau Van Hoang, head of Long Phuoc Ward's Anti-Sand Exploitation Inspectorate.

His inspection team is composed of six members scattered over a large area. Sometimes they caught sand traders red-handed but could fine them only VND1 million ($50).

"Appropriaters are ready to take us on with stones or sharp weapons, or they just submerge their boats and disappear into the river," he said.

"They are so elusive, and we have captured only boats, not a single exploiter in person in the last three years," he added.

Vulnerable Red River

The section of the Red River that runs across Ha Noi has attracted many barges from nearby provinces like Bac Ninh, Bac Giang, Ha Nam and Ninh Binh that are scooping up sand.

Hong Van Commune in Thuong Tin District, Phu Thuy Commune in Phu Xuyen District and the area bordering Ha Nam and Hung Yen provinces, are full of barges on the river that are dredging the riverbed both day and night.

"This activity not only causes landslides on banks but also changes the river flow in rainy seasons, imperiling life on both sides of the river and damaging dykes and other riverside structures," said Pham Ngoc Tien, deputy head of Ha Noi's waterway traffic inspectorate.

Some areas along the river have been warned about the risk of landslides, including on the left bank in Long Bien District's Ngoc Lam Ward, where some houses have developed cracks, and in Chuong Duong Ward, where many houses are on the verge of being swept away due to landslides or high water levels.

Since the beginning of the year, the Ha Noi Waterway Traffic Police Department has uncovered more than 130 cases of illegal sand exploitation on the Red River.

"Every time they heard the engines of patrolling canoes, they bolted immediately to bordering provinces to escape," said Do Van Chuan, a senior inspector of the department.

"They abandoned their barges and jumped into the river when caught red-handed," he added, noting that some of them even attacked law-enforcement officials recklessly in an attempt to escape.

The Ha Noi People's Committee has asked involved districts to keep a close eye on landslides at riverbanks and evacuate residents from dangerous zones and consolidate weak sections of the left bank in Long Bien District's Ngoc Lam Ward.