Rescue efforts are underway after a deadly explosion at a coal mine in China's central Henan province.
The blast at the pit in Yuzhou killed 26 miners and left another 11 trapped underground.
State media said the mine had been hit by a "sudden coal and gas outburst" which unleashed tonnes of coal dust.
A rescue official told the China News Service it could take four days to reach the men and there was little chance they would be found alive.
China's mining industry is the most dangerous in the world - more than 2,600 miners were killed in accidents in 2009.
The government has shut down more than 1,000 illegal pits this year as part of efforts to improve safety standards.
The latest blast happened early on Saturday at the Yuzhou pit, which is owned by Pingyu Coal & Electric Co Ltd, the official Xinhua news agency reported.
The national work safety agency said the explosion occurred as miners were drilling a hole to release pressure from a gas build-up as part of efforts to decrease the risk of blasts.
The gas concentration inside the mine was reported to have been at 40%, which is 40 times higher than normal acceptable levels.
More than 70 rescuers are battling dangerous levels of gas and the risk of falling rocks as they work to free the trapped miners.
"There is not much of a chance that the 11 trapped miners could have survived and it will take three to four days to find them," said Du Bo, deputy director of the rescue operation.
Zhao Tiechui, head of the State Administration of Coal Mine Safety, had said on Saturday the missing men could still be found safely.
"All the trapped people under the mine can be located, and then we send people to those located places to rescue the trapped. I think our goal is clear," he said.
Relatives of the dead and missing miners have criticised the safety standards at the mine.
"This place is not even safe, they started operations even before it was ready," the mother of one missing miner was quoted as saying by the Associated Press.
"They don't care about the workers' safety, they only care about their production."
The brother of one of the miners killed said the pit should not have been operating as the ventilation system was not working.
There has also been official criticism of the mine owners, blaming them for ignoring safety warnings.
"Since you were planning to deal with the unsafe factors [at the mine], why didn't you stop the operation at other platforms first and then deal with it?," Luo Lin, head of the work safety administration, asked the owners in a press conference.
He said it was fortunate that explosion had not caused a fire, meaning most of the 276 people who had been working in the mine at the time had been able to escape.
China is heavily reliant on its mining industry, with coal supplying some 70% of its energy needs. Many of those employed in mines are migrant workers with limited training.
The central government has made improving conditions in the country's 25,000 coal mines a priority, and the number of deaths has fallen from nearly 7,000 in 2002 to 2,631 last year.
In April, 115 miners were rescued alive from a flooded mine in Shanxi province after spending more than a week underground.
The National Energy Administration (NEA) closed 1,539 small and dangerous coal mines this year as part of restructuring efforts, said Xinhua.
But safety rules have often been ignored in favour of profit, as the economy has boomed.