BAISE, Guangxi -- Rescuers drilled two ventilation holes about 170 meters into the ground on Sunday to help release gas from a flooded coal mine where 29 miners remained trapped for six days in southwest China's Guangxi Zhuang Autonomous Region.
High-gas density had impeded the search progress in the Nadu mine where the flood occurred at 1:15 p.m. on Monday trapping 57 miners.
A total of 21 miners escaped or were rescued, but 29 remained trapped without contact. Seven others died and their bodies had been recovered.
"Seeping water and cinder still blocked sections of the water-soaked mining lane to the No. 4301 work surface, where the workers were trapped," said Shang Dengying, the director in charge of accident investigation with the State Administration of Coal Mine Safety, after inspecting the mine shaft on Sunday afternoon.
Rescuers managed to locate the trapped miners' working area on Wednesday. However, the rain and high-gas density had slowed the rescue effort.
More than 2,000 people were involved in the rescue, which progressed slowly with shovels in the narrow mining lane.
Zhu Zhengping, a drainage expert in the rescue mission, said the water was about 1 meter deep in the work surface in the flooded mine on Sunday following days of pumping.
He said two groups of rescuers were approaching the work surfaces from different directions, but they weren't sure how close they were to the work area.
The mine has an estimated reserve of 2.98 million tonnes of coal and can produce 190,000 tonnes annually. It is fully certified.