Adriyusman, a disaster response official, also said that a dangerous concentration of methane gas was hampering efforts by rescuers to get to the miners trapped about 100m underground.

The miners were said to be using traditional methods with few modern safety measures in place.

According to the World Coal Institute, Indonesia has the largest coal reserves in the Asia-Pacific region behind Australia, India and China.

It is the world's second-largest coal exporter after Australia.