An official overseeing a grueling rescue at a collapsed Indonesian gold mine said that the voices of dozens of trapped miners are no longer being heard as the effort to reach them continued for a fourth day on Saturday.

Rescuers are currently not entering the mine in North Sulawesi's Bolaang Mongondow district while an excavator and other heavy equipment are working on it, Abdul Muin Paputungan said.

No one has been saved from remote mine located in steep terrain since Friday when the death toll stood at eight with 20 people rescued. Authorities believe about three dozen miners remain trapped.

"Since yesterday we have heard no more voices from inside. On this fourth day the signs of life faded away," said Paputungan.

"But we still try to save them even though at the moment it seems like a miracle if they can survive."

He said using the excavator is a precarious effort that requires a high level of caution to prevent new landslides in the mine or the excavator itself toppling into a ravine. More than 200 people from various agencies are involved in the rescue.

The unlicensed mine collapsed on Tuesday evening due to shifting soil and the large number of mining holes.

Informal mining operations are commonplace in Indonesia, providing a tenuous livelihood to thousands who labour in conditions with a high risk of serious injury or death.

Survivor Denni Mamonto, being treated at a hospital in Mobagu, said on Friday that he was working in the mine with a group of friends when the roof collapsed without warning and large rocks tumbled down on them.

"My leg was stuck, I was helped by two others and then three helped me lift the rocks off my feet, then another person from above helped me out," he said. "But my friends didn't make it, those who work together with me."