A giant drilling rig has bored through hundreds of feet of earth and rock to create a 76-cm wide vertical tunnel through which any survivors could be brought to the surface in special safety buckets.
The drilling operation is expected to reach the mine cavity sometime today, where the nine men are believed to be holding out in water as cold as 11 degrees Celsius some 300 feet underground.
The miners accidentally drilled into an abandoned works, releasing an estimated 50 to 60 million gallons of water into their own shaft.
They were able to alert a second group of workers who escaped.
The trapped men had been communicating with the surface by tapping on a pipe pumping air into their underground chamber.
However rescuers said the last distinct taps were heard around 11.30 a.m. (1530 GMT), yesterday.
They said that later signals may have been obscured by increasing activity at the site, which is located at Que Creek mine in Somerset County, 95 km southeast of Pittsburgh.
Families of the trapped men have been bused to the site to witness the rescue operations.
