Iftikhar Ahmed, a top mine inspector, said Sunday's accident occurred at a mine in Balochistan province, some 40 km east of the provincial capital, Quetta. The mine is owned by the state-run Pakistan Mineral Development Corporation but leased to a contractor.

Ahmed said the mine was declared dangerous two weeks ago, but the warning was ignored. Rescue workers are trying to reach the trapped miners, but the presence of methane gas is hampering their efforts.

Such explosions are not uncommon in coal mines in Pakistan, most of which are located in Balochistan and neighboring Sindh province, where safety measures can be lax.

The country has huge coal reserves estimated at more than 184 billion tons. It produces 4 million tons of coal annually, most of which is consumed by brick-making kilns.