The incident occurred on April 21 along a stretch of the left-bank dyke in Phong Chau Ward, where the ground sank by 50-70 cm, causing wide fissures in house walls and roofs.
Local authorities said the subsidence was progressing rapidly, with some homes at risk of collapse due to underlying geological instability, making remediation difficult.
All affected households have been evacuated, with some staying with relatives while others are being assisted by local authorities.
Police and military forces have cordoned off the area, set up warning signs and are maintaining round-the-clock monitoring.
The cause of the incident is under investigation.