Reporters and residents counted approximately 12 visits by large dredging vessels to a stretch of the Lam River in Vietnam's Nghe An province between about 19:00 local on October 4 and dawn on October 5, according to an investigation by Vietnamese newspaper Thanh Nien.
The vessels extracted sand beside Hung Lam Two hamlet in Hung Nguyen Nam commune, well away from two licensed sand mines. One mine is in Nghe An and the other is in neighbouring Ha Tinh.
Reporters observed vessels pumping close to houses and continuing to pump while moving along the river. Some large vessels were travelling without lights.
Each vessel lowered between two and six suction hoses into the riverbed, depending on its size. Residents estimated their capacity at 120 to 200 cubic metres each.
On the afternoon of October 4, three vessels extracted sand in daylight. They moved farther from the bank when they noticed filming but kept pumping until their holds were full.
Residents have been keeping overnight watches and direct powerful torches at vessels approaching the bank. The vessels move towards mid-river without stopping their pumps.
"Sometimes we have to throw stones at the cabin, and only after hearing the clanging sound will the boat leave," a resident identified told the newspaper. "They are dredging right behind our houses, dredging so close to the shore that the embankment will be washed away, and landslides will threaten our homes."
An unnamed licensed mine owner said he sometimes used his own boat at night to drive away illegal dredgers. He feared their activities would affect his licensed extraction area.
According to a follow-up report, authorities seized three vessels on the night of October 6, after the newspaper supplied its findings and photographs. On Friday, October 16, commune leaders said the vessels remained detained.
Residents said extraction resumed after a few nights, although vessel visits were less frequent.
"Despite taking vigorous action, we still have not been able to stop it completely," said commune chairman Cao Anh Đức.
Commune police said operators exploited darkness, rain and poor visibility. Residents said lookouts posted along the river dyke warned dredgers when patrol boats set out.
The local embankment is built with concrete, rubble stone and gabions. It shows substantial deterioration, with collapsed sections and exposed gabions.