Chinese rescuers drilled several new holes on Tuesday to help them reach at least 12 gold miners trapped underground for nine days, as dwindling food supplies and rising waters threaten their survival.
Twenty-two workers became stuck 540 metres underground at the Hushan mine near Yantai in China's eastern Shandong province after an explosion damaged the entrance.
After days without any sign of life, some of the miners sent a message to the surface using a metal wire rescuers dropped into the mine on Sunday.
The handwritten message said a dozen of them were alive but surrounded by water and in need of urgent medical supplies.
Several of the miners were injured, the note said.
A subsequent phone call with the miners revealed 11 were 540 metres below the surface and another miner – apparently alone – was trapped a further 100 metres down.
The whereabouts and condition of the other 10 miners is unknown.
Rescuers have already dug three channels and sent food, medicine, paper and pencils down thin shafts – lifelines to the miners.
But progress was slow, according to Chen Fei, a top city official.
"The surrounding rock near the ore body is mostly granite ... that is very hard, resulting in slow progress of rescue," Mr Fei said on Monday evening.
"There is a lot of water in the shaft that may flow into the manway and pose a danger to the trapped workers."
Mr Fei said the miners only had enough food for two days.
Rescuers drilled three more channels on Tuesday, according to a rescue map published on the Yantai government's Weibo account.
Footage from state broadcaster CCTV showed dozens of rescuers clearing the main return shaft, while cranes and a massive borehole drill was used to dig new rescue channels to reach the miners.
Rescue teams lost precious time because it took more than a day for the accident to be reported, China Youth Daily reported, quoting provincial authorities.
Both the local Communist Party secretary and mayor were sacked over the 30-hour delay in and an official investigation is under way to determine the cause of the explosion.
Mining accidents are common in China, where the industry has a poor safety record and regulations are often weakly enforced.
In December, 23 miners died after being stuck underground in the south-western city of Chongqing.
Sixteen others died from carbon monoxide poisoning after being trapped underground at another coal mine in the city months earlier.
