SAWAHLUNTO, Indonesia – A coal mine explosion in Indonesia's Sumatra island has killed 28 miners and 12 others are missing, officials said Wednesday.

The explosion, Tuesday, may have been caused by a build-up of methane gas in the mine in Parambahan, West Sumatra. The miners have been trapped underground for around 30 hours.

Rustam Pakaya, the head of the health ministry's disaster center, said in a telephone text message that 28 had been confirmed dead, 8 were still in hospitals, one had been discharged and 12 were missing.

Local police chief Jasman, who like many Indonesians uses one name, said the prospect of finding more survivors in the mine, which according to media reports is 150 meters (500 ft) deep, were fading.

Indonesia has rich mineral resources with many coal and other mines, but often tends to use open-pit mining rather than underground mining.

The mine hit by the explosion was locally owned and produced only about 1,500 tonnes of coal a month and supplied local paper and power companies.

Indonesia, which is the world's largest thermal coal exporter, is expected to produce around 230 million tonnes of coal this year, according to a government estimate.

(Additional reporting by Telly Nathalia and Sunanda Creagh in Jakarta, Writing by Ed Davies)