Indonesian authorities have warned that up to 100 people could still be trapped and feared dead inside a collapsed gold mine despite a painstaking rescue effort that has so far plucked 19 people alive from the rubble but also seen nine deaths.

Search teams at the unlicensed mine on Sulawesi island have been hampered by steep terrain, unstable soil and dangerously narrow mining shafts since a landslide caused the accident on Tuesday.

While authorities said the search-and-rescue effort would continue for another week, they made no mention of continuing efforts to get food and water to any possible survivors.

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National disaster agency spokesperson Sutopo Purwo Nugroho said the number of miners inside the shafts at the time of the accident was still not known as survivors had given varying tallies.

“Some say 30 people, 50, 60 people – even 100 people, because at the time there were many in the main pit [and] … an unknown number in the smaller ones,” he said in a statement.

Because of the precarious conditions, rescue workers initially had to dig by hand to try to reach any survivors, but relatives of those trapped last week gave permission for heavy-duty machinery to be deployed.

Although mechanised diggers cleared debris from the entrance of one hole on Sunday, they found no more survivors.

The accident happened in the Bolaang Mongondow region of North Sulawesi, where five miners were killed in December after a similar illegal gold mine accident.

Mineral-rich Indonesia has scores of unlicensed mines – many with complete disregard for even the most basic safety procedures.

In 2015, 12 people died when a mineshaft collapsed on Java island, and 11 miners died on Sumatra island when a mudslide engulfed a mine in Jambi province.

The following year, 11 miners died after a mudslide engulfed an illegal gold mine in Sumatra’s Jambi province.