Rescue teams are trying to drain water from the flooded mine
Nearly 1,000 rescuers are working around the clock to reach scores of coal miners trapped in a flooded pit in northern China, state media says.
But it could take them days before they reach the 153 miners.
A total of 261 people were in the mine in northern Shanxi province when water rushed in. More than 100 managed to escape but the rest were trapped.
Safety standards have improved over recent years, but China's mines are still the most deadly in the world.
The workers in this latest accident have been trapped since Sunday, but there are unconfirmed reports that water started to leak into Wangjialing mine a few days before.
Additional pumps have now been taken to the state-run colliery - which is still under construction - to get rid of the water.
Rescuers have also started drilling a hole to open up a drainage channel to divert the flood water.
But water is not the only problem.
"The coal mine has a high concentration of gas. Rescuers have to face the danger of toxic gas, while fighting the water," Liu Dezheng, spokesman for the rescue effort, told the state-run Xinhua news agency.
No one knows for sure if the miners, thought to be trapped in a number of underground locations, are dead or alive.
President Hu Jintao and Premier Wen Jiabao ordered local authorities to spare no effort to save them, Xinhua said.
The mine covers 180 sq/km (70 sq miles).
Most of those trapped in the shafts are migrant workers from Shanxi, Hebei, Hunan and Guizhou provinces, a rescuer said, quoted by Xinhua.
As rescue efforts continued, Xinhua announced that two workers trapped in another flooded mine, in Henan province, were pulled out alive on Tuesday - eight days after their mine was inundated
But earlier this month rescue efforts for 31 miners trapped when a coal mine flooded in the Inner Mongolia region of China were halted after two weeks when no sign of life was found.
According to official figures, 2,631 coal miners died in 1,616 mine accidents in China in 2009, down 18% from the previous year.