Torrential rain triggered a landslide late on Friday in a small-scale mine run by local residents in the Arfak mountains in West Papua province, said Abdul Muhari, the spokesperson of Indonesia’s disaster mitigation agency.

The landslide hit temporary shelters used by the miners and killed at least one person and injured four with 19 others still missing, he added.

At least 40 rescuers with police and military personnel had been deployed to search for the missing, officials said.

Small-scale and illegal mining has often led to accidents in Indonesia, where mineral resources are located in remote areas in conditions difficult for authorities to regulate.

The rescuers started the search operation only on Sunday because it took at least 12 hours for teams to travel to the site, Yefri Sabaruddin, the head of the local rescue team, told Reuters on Monday.

“The damaged roads and mountainous tracks as well as bad weather hampered the rescue efforts,” Yefri said.

The number of casualties could rise, he added.

At least 15 people died in the collapse of an illegal gold mine in West Sumatra province September last year after a landslide caused by heavy rains.

Another landslide in a gold mine on Sulawesi island killed at least 23 people in July last year.