A 150m section of the Hong (Red) River embankment in Phu Thinh Ward in Son Tay Town collapsed on Monday, dumping three workshops and two diggers into the water.
No casualties were reported. The landslide affected a 3,000-sq.m area.
Officials from the local Dyke Management Unit blamed illegal sand exploitation for the incident.
Do Duc Thinh, director of the municipal Flood Control and Dyke Management Department, said this was the first incident of its kind in the area.
"It is dangerous now because the landslide area is just 30-40 metres from the dyke's footing," Thinh said.
He added that a team of dyke experts had been sent to the area to reinforce the river banks.
Ha Noi authorities asked Son Tay Town People's Committee to evacuate all residents in the area and to close off roads to traffic. Danger signs have also been put up.
"I inspected the area and found that many residents are refusing to leave their houses," Thinh said.
The municipal Department of Agriculture and Rural Development has been asked to survey the area and report its findings to the Ha Noi People's Committee.
Barges from the nearby provinces of Bac Ninh, Bac Giang, Ha Nam and Ninh Binh repeatedly steal sand from the area, officials said.
"Such activities cause changes in the flow of the river during the rainy season, imperilling life on both sides of the river and damaging dykes and other riverside structures," Thinh said.
So far this year the Ha Noi Waterway Traffic Police Department has uncovered more than 130 cases of illegal sand exploitation on the Red River, he said. — VNS