Small-scale and illegal mining has often caused accidents in Indonesia, where mineral resources are located in remote areas in conditions difficult for authorities to regulate.
The illegal gold mine in the district of Solok collapsed after a landslide on Thursday evening due to heavy rain, said Irwan Efendi, the head of the provincial disaster agency.
Rescuers must trek eight hours to get to the site, which is inaccessible by road, Irwan told Reuters, adding, "The victims are the residents who manually mine for gold."
He estimated there were probably 25 people in the mine at the time of the incident, of whom 15 died, while three were injured and seven are missing.
Police and military launched a search early on Friday for the missing, along with steps to evacuate the dead.