The blast occurred in a mine run by the state-owned Pakistan Mineral Development Corporation (PMDC) in Surran range, some 35 km (22 miles) east of the provincial capital, Quetta.

"We don't know about casualties right now. Rescue workers are busy in their work. Some 30 workers were inside the mine at the time of the blast," a senior PMDC official told Reuters.

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

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