The accident occurred at around 5 pm at a stone quarry operated by Anh Tuan Co. Ltd. in Cam Tu Commune, according to local officials.
Three workers from Lao Cai Province were working at the foot of the mountain when a large volume of rocks and soil suddenly collapsed onto the site.
One victim died on the way to hospital, while two others remain missing.
Authorities deployed firefighters, soldiers and rescue teams along with specialised machinery to search for the missing workers.
Rescuers also used sniffer dogs, drones and infrared thermal detection equipment to assist search efforts at the scene, where there remained a risk of further landslides.
Local authorities, police and military representatives were present at the site to oversee rescue operations and investigate the cause of the accident.