The incident took place in the Dhanbad district of the eastern state of Jharkhand late on Wednesday.

As many as 57 miners had entered the mine in the western Jharia area, about 170km north of state capital Ranchi, when a blast to open up a new mining area caused the roof collapse, releasing deadly methane gas, the official said.

"This is an unprecedented situation and the chances of their survival are zero," Partha Bhattacharya, chairman of Bharat Coking Coal Limited, a state-run firm which owns the mine, said on Thursday.

"The miners were working at a depth of 460 metres when the explosion and the gas leak reduced the oxygen level to almost zero."

Rescue operations were launched overnight, but Bhattacharya said rescuers had only been able to get past level three of the 18-level mine. The 54 miners were believed to be trapped in the last level.

Tough task

Rescuers said a fire in the mine, triggered by the blast, had made their task tougher.

"We can't breathe at all," one rescuer said.

Three miners who were rescued complained of severe breathlessness.

"The explosion was so powerful that I was thrown off my feet and I saw a trolley loaded with coal get ripped apart and break up," said Nunu Lal, one of the rescued miners.

Every year, hundreds of miners get trapped inside mines in India, where safety standards are seldom met by authorities.

Last month, several miners were trapped during an illegal mining operation in the neighbouring state of West Bengal, but a search for them was abandoned after water from a river flooded the pit.

Series of fires

The Jharia area is home to coalfields with prime coke coal. Mining in the region began in the 19th century but the mines have been hit by a series of underground fires that have raged since 1916.

Experts blame the fires on unscientific mining and illegal extraction of coal in the past and warn that it is an environmental disaster waiting to happen.

Bharat Coking Coal, headquartered in Dhanbad, produces the bulk of India's coking coal and meets nearly half of the prime coal needs of India's steel sector. It also supplies coal to power stations in the northern regions.