Rescuers are assembling a hydraulic bore in preparation for months of drilling a shaft big enough to rescue 33 trapped Chilean miners, some of whom are showing signs of depression.
The bore drills at a maximum rate of 20 metres per day. The initial narrow shaft it will dig will have to be doubled in diameter to permit a man to pass through.
Once it is fully assembled and operational, engineers said it will take up to four months of painstaking drilling to reach the miners, who are trapped 700 metres down the gold and silver mine that collapsed on August 5th.
Most of the miners were in good spirits in a 45-minute video they sent to their families at the surface after their three-week ordeal, but a handful of them appeared to be struggling psychologically, officials said last night.
"Five of the miners are isolated, are not eating well and do not want to appear on camera," Chilean health ninister Jaime Manalich said. "This is what we call depression."
The minister said a psychiatrist would attempt to treat the men over an intercom system dropped to them.
The mental problems emerging among the miners holed up in a hot and cramped shelter they themselves have described as "hell" augured badly for the months of continued captivity the men have yet to endure.
During that time, the men were to receive water, sustenance, medical care and communication through a tiny drill probe hole that located them last Sunday.
The video footage shot by the miners and broadcast in Chile earlier this week showed most of the group were coping with their confinement.
"We've organised everything really well down here," one of the miners, sporting a scraggly beard and pointing to a corner reserved for medical supplies, said in excerpts of the video.
"This is where we entertain ourselves, where we have a meeting every day, where we make plans. This is where we pray," he added.
About a dozen other miners waved at the mini-camera, which was delivered via one of the metal capsules dropped to them regularly.
Chilean authorities have already taken steps to boost the men's mental resilience for the ordeal that still lays ahead.
Four officials from Nasa are due to arrive in Chile in the coming days to provide expertise, while submarine commanders in Chile's navy have already given advice.
At least five people from a group of 16 who survived 72 days in the Andes after a 1972 airplane crash by eating dead passengers were also to head from Uruguay to the scene of the mine rescue drama next week.
"When they get out and they hug each other above ground, they'll see how little two or three months is in a lifetime," said one of the crash survivors, Jose Luis Inciarte, (62).
As rescue operations and psychological assistance ramped up, so did legal actions against the owners of the mine where the men are trapped.
San Esteban Mining, the company responsible for the gold and copper mine in northern Chile, was ordered by a local judge to freeze $1.8 million in revenue so that it can pay future compensation to 26 of the families of those trapped.
One family has also filed a lawsuit over the incident, accusing the mine company and government inspectors of criminal negligence by allowing the facility to reopen in 2008 after a worker accident led to its closure in 2007.
Chile's mining minister announced last night he will revise mine safety regulations and more than double the budget and staff monitoring the sector in the wake of the collapse.
"We can't guarantee there will be no more accidents, but we can make company leaders more aware of the importance of worker safety," Laurence Golborne told reporters.