Chinese rescue teams say it could take more than two weeks to rescue a group of miners trapped hundreds of meters underground.
They were trapped after an explosion closed the entrance tunnel to the Hushan gold mine in Shandong province on January 10.
Authorities contacted 11 surviving miners a week after the blast, but one died.
Rescuers drilled small holes to deliver food and medicine to the men.
The cause of the explosion, which sealed the entrance to the mine, is still unknown.
The fate of 11 other miners caught in the blast is unclear – authorities have failed to communicate with them, although they have cut food and communications in other areas of the mine.
The group, found alive, told rescuers that they had established communication with a lone miner about 100 meters below them, but have since lost contact with him.
How will the rescue work?
Rescue operations are currently trying to widen the narrow shaft to make it large enough to lift the miners.
However, drilling is difficult, as it has to pass through particularly hard granite and the miners are trapped far from the surface. Rescuers face an additional problem as the mine is soaked and there is a risk that the chamber in which the miners are stuck will flood.
“The obstacles are too big, which means we need at least another 15 days or even more to get to the miners,” said Gong Haitao, deputy head of the local publicity department.
The debris standing on the road weighs about 70 tons, he added.
How did they fall into the trap?
The entrance to the mine was severely damaged and communication was interrupted by a hitherto unexplained explosion.
For a week there was no sign of life. Then, last Sunday, rescuers felt the pull of one of the ropes that descended into small shafts leading down into the dark.
A paper rope note was then sent from a group of 12 surviving miners – 11 trapped in one place and 12 trapped below.
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Contact with the 12th miner has since been lost, while one of the group of 11, who fell into a coma after receiving a head wound in the blast, was confirmed dead on Thursday.
Mining accidents are not uncommon in China, where industrial safety regulations may be poorly enforced. In December last year, 23 miners died after a carbon monoxide leaked into a coal mine.
In September, 16 workers were killed in another mine on the outskirts of Chongqing, also due to carbon monoxide. In December 2019, an explosion at a coal mine in the province of Guizhou, southwestern China, killed at least 14 people.
How do miners cope?
The group of 10 known survivors are locked in the dark about 600 meters underground. They are in regular contact with rescue teams.
A communication line has been established and food and medicine can flow to them through a narrow shaft.
While receiving porridge and food liquids, the miners a few days ago asked for a traditional dish of sausages.
Eight of them are thought to be doing well, while two are in poor health.
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