Hopes for a sign of life from the six miners trapped underground in a coal mine in the western state of Utah seemed to wane on Friday.
Rescuers had managed early on Friday morning to send a microphone through a 6-centimetre wide hole and a 500-metre pit down into the mine, where the men were suspected trapped.
However, the microphone did not transmit any sounds.
Nevertheless, experts were still hoping to find the six men alive after the mine collapsed on Monday.
Measurements had shown that the air in the mine was very good - good enough to breathe, the owner of the mine near Huntington, Robert Murray, said.
These were very good news, he said: "It means, that if they are alive they'll stay alive."
Dennis O'Dell of the US miners' union, meanwhile, told CNN it was possible that the miners had been too far away from the microphone to even know it existed, given the size of the mine.
"We still have reason to hope," O'Dell said.
While the microphone stayed in the mine on Friday, rescue workers were drilling a second hole with a larger diameter, hoping to break through the mine's ceiling by Saturday morning GMT at the latest.
The rescuers were planning to send a rotating video camera through the slot down into the mine and later also food for the missing men.
Rescue teams were also digging further through the collapsed tunnel towards the miners, who are suspected trapped 6.5 kilometres off the mine's entrance in complete darkness and cold.
Murray thinks the miners could be reached by Tuesday.
The tunnel collapsed on Monday for yet unexplained reasons.
Murray insists that an earthquake was the cause, but geologists believe that their seismological equipment picked up the tunnel's collapse, which was then registered as ground motion.
Last Mod: 10 Ağustos 2007, 16:10