Engineers drilling to reach 33 trapped miners in Chile say the men might be rescued as early as this weekend.
The head of one of the drilling operations, Pedro Buttazzoni, told the BBC his drill had only 160m (524ft) further to go to reach the men.
However, the man overseeing the entire operation has been more cautious about the timetable for their rescue.
The miners have now been trapped underground for two months, longer than any previous group.
Buttazzoni, the head of the Chilean mining company Geotec, said his drill had already cut through 464m (1,500ft) of rock.
He said his team expected to break through to the area where the miners are sheltering in 3-4 days.
And he said rescuers were debating whether they would in fact need to line the rescue tunnel with metal casing as planned, a process that would take several days.
If it was decided that the lining was not needed, it was “perfectly possible” that the miners could be brought to the surface by the weekend, he said.
The timetable for rescue has shortened dramatically as the three drills racing to reach the miners have made rapid progress.
Last week the government said the rescue attempt would begin in the second half of October, having previously said it would start in early November.
President Sebastian Pinera now says he hopes the miners are rescued before he travels to Europe on 15 October, saying he wants to “share that moment with the miners”.
But told of that comment, rescue chief Andre Sougarret said he had no new information to suggest a rescue would be possible before the second half of the month.
A sports physician who is in daily contact with the miners, Jean Romagnoli, told the BBC the men were “very cheerful” and eagerly awaiting their imminent rescue.
But he said it was vital that they continued their fitness training, because pulling them up to the surface would be very stressful.
“That’s very dangerous. We want to prevent any type of overheating, because that can produce thermal shock, when your temperature rises above 42C [108F], which decomposes the protins and you can have a hard time recovering.
“That could be fatal,” he said.
Once the rescue shaft is complete, a specially made steel capsule, designed by the Chilean navy, will be lowered.
It is expected to take an hour to pull each of the trapped men to the surface.
The miners have even begun to send prized possessions and mementos which they don’t want to leave behind up to the surface using small capsules, known as “doves,” in which they have been receiving supplies through narrow boreholes. (BBC)
