A blast at a coal mine has killed at least 34 workers in southern Pakistan, the provincial disaster agency said, adding that rescuers were searching for more missing miners.

Officials said the blast occurred at a private coal mine in the afternoon in the Sorange coalfield, located about 30 kilometres northeast of the provincial capital, Quetta.

Soon after the explosion, a fire broke out inside the mine, causing parts of the structure to collapse. The blast was heard over a wide area of Sorange.

"According to information received from the deployed teams, 34x Dead bodies have been recovered," southern Balochistan's provincial disaster management authority said in a statement on Friday.

Chief Inspector of Mines Muhammad Atif said the explosion was believed to have been caused by the accumulation of methane gas at a depth of around 1,200 metres, triggering a fire and filling the mine with hazardous gases. He said most coal mine explosions in Balochistan occurred due to the presence of methane gas.

Mining engineers and workers created alternative routes to access the affected mines, but the presence of large quantities of methane gas and the ongoing fire created major hurdles in reaching the bodies and trapped miners deep underground.

Deadly accidents are common in Pakistan's coal mining industry, particularly in Balochistan, where many mines lack adequate ventilation, gas monitoring systems and other basic safety measures.

Mine workers and labour groups have long accused mine owners of failing to enforce safety regulations or provide adequate protective equipment.

Despite the risks and low wages, thousands of miners depend on the coal industry for their livelihoods in Balochistan, Pakistan's largest but least developed province, where unemployment and poverty remain widespread.