Four children, all students at a local primary school, were playing on a local hill at around 4 p.m. when the landslide occurred.
Authorities and locals soon arrived on the scene to attempt a rescue. Three children, aged 6, 9 and 10, were found dead. One was saved.
The landslide happened next to a mine that has been abandoned for years and is being demolished.
Tran Van Thang, chairman of Thuong Am Commune People's Committee, on Friday said the children's fathers were all involved in the mine's demolition.
An investigation is ongoing.