The incident occurred at around 11.05 am on August 10 in Trung Son Ward, according to a report by the ward administration.
Residents said they heard a loud explosion accompanied by tremors from the direction of the Mai Mountain quarry before rocks broke loose from the mountainside and rolled towards nearby homes.
An inspection found several large rocks had fallen into the grounds and buildings of a house belonging to Dinh Thi Lua, whose property borders the mountain.
Officials also observed several large rocks near the summit that appeared unstable and could pose a further rockfall risk.
No one was injured, but the rockfall severely damaged parts of a 3.5-storey house, including its structural elements, swimming pool area, balcony and fence, as well as parts of the garden and a water tank. Trees in an adjacent forest area were also damaged.
The affected property is more than 200 metres from a quarry operated by a local construction and trading company.
The company said it had carried out blasting for mineral extraction shortly after 11 am that day. However, it has not been determined whether the blasting was linked to the rockfall.
The household has been asked to leave the affected area unchanged while officials investigate the cause and assess the damage. Residents have also been told not to live, work or conduct business in the danger zone until safety risks have been addressed.
Relevant agencies are reviewing land and construction records for the property as well as documents related to the company's mining operations.
Trung Son Ward has asked provincial agencies to conduct a geological survey of Mai Mountain, assess its stability and address the risk of further rockfalls.
It has also requested an inspection of the company's mining, land use and environmental practices.
Local police have been asked to investigate the cause of the rockfall and determine whether any regulations on workplace safety, environmental and natural resource management or the use of industrial explosives were breached.
