Jakarta - An explosion rocked a coal mine in the Indonesian province of West Sumatra on Tuesday, killing at least seven people, with more than 20 others trapped inside, media reports said.

The cause of the blast was not immediately known, Sawahlunto district police chief Adjunct Commissioner Jasman said the explosion may have been caused by methane in the mine. He confirmed that seven people were killed in the accident.

Jasman told the Jakarta-based Elshinta private radio that around 24 people were still trapped inside the mine and their fate remained unknown.

Another report by MetroTV television station said up to 30 people were trapped inside the mine, which is operated by the state-run Bukit Asam coal mining company.(dpa)