Liu Dezheng, a spokesman of the rescue headquarters, said the men trapped in the flooded Wangjialing mine had been working in nine different platforms when water gushed in, and some of the platforms were above the underground water level.

"It is believed that some workers may have a chance of survival," the official Xinhua News Agency quoted Liu as saying late on Wednesday.

"We will go all out to save them."

So far, there has been no contact with the trapped miners, however.

Flouting rules

More than 1,500 rescue workers have been tunnelling and laying pipes around the clock since Monday to drain away water from the unfinished pit.

On Wednesday a government safety body said the flooding at the Wangjialing mine was triggered after tunnelling workers broke through into an old shaft filled with water.

A preliminary investigation found that the mine's managers caused overcrowding in the shaft by assigning extra tunnelling crews in a rush to finish the work, and ignored warning signs, the State Administration of Work Safety has said.

Two miners were killed in a mine blast in Henan province, the third incident this week [Reuters]

"Water leaks were found numerous times on underground shafts," it said, but the mine's managers "did not take the actions necessary to evacuate people".

Relatives and co-workers of the trapped miners criticised rescue efforts for being too slow, and have demanded quicker action.

It could prove the deadliest mine accident in China since a coal mine flood in eastern Shandong province in August 2007 killed 172 miners.

The latest disaster is a setback to recent, significant improvements in Chinese mines. They are the world's deadliest, claiming thousands of lives each year.

A few later, an unfinished coal mine in the far-western Xinjiang Uighur Autonomous Region collapsed, trapping a group of construction workers underground.

Lifted to safety

Rescuers worked for a second day on Tuesday to free the 10 workers trapped in the Shajihai coal mine.

Another 11 workers were lifted to safety and taken to hospital, official media said, adding that the cause of the collapse is under investigation.

The mine, owned by the Luneng Coal-Electricity Development Company Limited, was due to start operation in October 2011, with an annual capacity of 900,000 tonnes, the China Daily said.

China has the world's deadliest coal-mining industry, with more than 2,600 people killed in mine floods, explosions, collapses and other accidents in 2009 alone.

Compared with other manual jobs, Chinese coal miners can earn relatively high wages, but risk their lives facing the danger from floods, explosions, gas and cave-ins.