Chinese mines have a terrible safety record
More than 70 people are now known to have died in Tuesday's gas explosion at a mine in eastern China.
Officials said they held up little hope that a further 15 men still registered as missing would be found alive.
The accident happened in the state-registered Luling mine, near the city of Hefei in Anhui province, 950km (600 miles) south of Beijing.
There were 113 people in the mine at the time of the blast, working 500m (1,500 feet) underground.
The cause of the accident is still being assessed, but investigators said the mine ventilation system malfunctioned, and levels of toxic gases exceeded security standards.
Rescue work has been impeded by flooding and high levels of explosive gases, according to the official Chinese Xinhua news agency.
"It's not easy down there. Each team is facing much
uncertainty in the mine. They still haven't located the exact place
of the gas explosion," an official at the State Administration for Work Safety told the French news agency AFP.
Xinhua said an immediate security overhaul of all mines had been ordered to prevent similar disasters.
The safety record of Chinese mines is one of the worst in the world.
According to Beijing's work safety bureau, at least 4,500 fatalities occurred in China's coal mines last year, although unofficial estimates put the figure as high as 10,000.
Explosions are common, due to poor ventilation which fails to clear natural gas which seeps from coal seams.
Deficient safety equipment and lack of fire-fighting apparatus compound the dangers.
Many such incidents occur in privately owned mines, which lack operating licences and adequate safety equipment.
China relies heavily on the coal industry for its energy needs.