Rescuers estimate that it will take at least two more weeks to release miners trapped underground in China for 12 days already, despite the frantic continuation of drilling operations on Friday, according to state media.
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A total of 22 workers at a gold mine in Qixia, in eastern Shandong province, were trapped on January 10 following an explosion that blocked exits and cut communications.
A minor died this week from his injuries.
Ten are about 580 meters deep and communicate by telephone with the surface.
Rescuers have no news of the remaining 11 men.
Drilling operations are complicated by the geological structure of the soil, made up of particularly hard rocks like granite, according to public television CCTV.
“
The obstacles are too great.
We will need at least 15 additional days, or even more, before reaching the minors
"Gong Haitao, deputy director of the local authorities' communications department, told the channel.
Thanks to a metal cable lowered through a conduit dug in the rock, rescuers were able to transmit food, medicine and phones to the group of miners trapped 580 meters underground.
They were thus able to regain their strength.
To extract the men, rescuers are currently trying to widen one of the wells.
Several other conduits are also being drilled.
CCTV on Friday released footage of several piles of debris dug out of the ground and a powerful drill rig in action.
The group of 10 miners have tried to spot the missing men, using lasers and loudspeakers, but so far without success, the China New News Agency said.
Presence detectors and nutrient solutions had already been brought down by rescuers in other sections of the mine in an attempt to find them.
While mine safety has improved significantly over the past decades, accidents still occur regularly in China, where regulations are sometimes not enforced.
In December, 23 miners were killed in a coal mine in Chongqing (southwest).