A series of methane gas explosions at a coal mine in Pakistan has killed at least 19 and trapped more than 30 people.

Three explosions occurred at a depth of 4,000m on Sunday, causing a collapse.

About 15 days before the explosions, the government warned PMDC to stop mining as there was danger of explosion due to an accumulation of methane gas.

Initial rescue work was delayed as emergency services equipment was not available at the mine and had to be brought from Quetta City.

Miners from nearby coal mines started rescue work on their own, and were able to rescue four miners and retrieve nine dead bodies.

Though efforts are being made to rescue more than 30 miners still trapped in the mine, there is thought to be little chance of their survival.

The coal mine, located about 30km from Quetta City in Balochistan Province, is run by government-owned Pakistan Mineral Development Corporation (PMDC).