An Australian drilling consultant says it is likely 33 miners trapped deep in a Chilean mine may be there until Christmas.
The miners have been trapped at the San Jose copper and gold mine, near the city of Copiapo since 5 August and were discovered alive and well 17 days after the cave-in.
Rescuers made contact with the men on Sunday after lowering a probe 700 metres beneath the surface.
Drilling consultant Kelvin Brown, who has been helping with the rescue attempt, told Radio New Zealand's Checkpoint programme the miners know it will take a while before they are freed.
"They already know that it will take a long time - they're underground miners, they're well aware of what has to happen to get to them."
The BBC reports engineers are preparing to install a large drill to dig a new bore hole to rescue them and specialised equipment has arrived.
Capsules containing the supplies of glucose, rehydration tablets and medicine are being sent down a tube to the miners, which is their only lifeline.
Relatives have set up shrines to their loved ones at the surface of the mine, adorned with photographs and personal messages of support.