A camera lowered into a mine cavity where six Utah miners are believed trapped has detected no signs of life.
However, a US mine safety expert said the images did reveal a "survivable" chamber, with the roof intact and drinkable water on the floor.
But dirt on the lens obscured the view, and a steel lining must now be inserted into the bore hole before the camera is lowered back into the cavity.
No contact has been made with the men since a tunnel collapsed on Monday.
Rescuers drilled a 9in-wide (23cm) hole into a cavity at the Crandall Canyon mine early on Saturday, allowing them to lower in a high-resolution camera to check for signs of life.
"The good news is that we do have evidence of a 5.5ft-deep cavern... We found a survivable space," said Mine Health and Safety Administration chief, Richard Stickler.
However, rescuers said they were "disappointed" that no-one had responded to repeated tapping signals.
Air tests
It is hoped the re-inserted camera will be able to scan 100ft (30m) in each direction, providing a clearer idea of conditions.
Mine officials are refusing to give up hope of finding the men alive, saying they may have moved to another area.
CRANDALL CANYON MINE
"It's always been a rescue mission... but it's just too slow," said Bob Murray, head of Murray Energy Corporation which co-owns the mine.
The miners were trapped 1,500ft (457m) underground and about 3.4 miles (5.5km) from the entrance to the mine, near the town of Huntington, 140 miles (225km) from Salt Lake City.
Tests carried out after a smaller hole was drilled into the mountain late on Thursday showed no sounds of human activity and levels of oxygen insufficient to support human life.
Initially the collapse was blamed on an earthquake, but experts have since suggested the shafts might have caved in with enough force to register on seismographs.
This has led to speculation that mining procedures could have triggered the incident.
It has been claimed the workers were using a risky technique known as "retreat mining", where the last standing pillars of coal are pulled down and the roof is allowed to fall in.
But Mr Murray has rejected that, insisting that an earthquake caused the collapse and that the mine was run safely.
US federal mining inspectors have issued 325 citations for alleged safety violations at the mine since January 2004. Of those, 116 were considered "significant and substantial" and likely to cause injury.
However, some experts have said the number of citations is not unusual.
^ Back to top | BBC Sport Home | BBC Homepage | Contact us | Help | ©
~RS~q~RS~~RS~z~RS~18~RS~)