Authorities in Indonesia have stated that up to 100 people could still be stuck in an illegal mine that collapsed and led to the deaths of at least nine people so far.

Since the collapse of the illegal mine in Sulawesi on February 26, search efforts have been hindered by a combination of steep terrain, narrow mining shafts and unstable soil, AFP reported. 

Sutopo Purwo Nugroho, a spokesperson for the National disaster agency, said the number of miners trapped had still to be determined as survivors had given varying numbers, with some saying 30, 50 and even 100. 

Initially, rescuers conducted the operation by digging with their hands, but last week relatives of the trapped victims gave the rescuers permission to use heavy-duty machinery. Rescuers cleared debris from the entrance of one hole on February 24 using machinery, but found no survivors.

Unlicensed mines have been a problem in mineral-rich Indonesia. Safety standards are often disregarded. 

Read: Indonesian gold mine death toll rises to seven

Read: At least three dead in illegal gold mine collapse