MIDDELBURG – At least six people were killed after a gas explosion in a coal mine in South Africa’s eastern province of Mpumalanga on Thursday, Radio Pakistan reported.

According to South African state media, about twenty miners were trapped underground at the mine in Middleburg.

Rescue efforts were hampered by dangerously high levels of toxic gas underground.

Police spokesman Leonard Hlati said that several people had entered the mine on Wednesday afternoon to steal copper wires that supply electricity for lighting and ventilation when a gas pipe exploded.

Copper is often stolen from disused mines in South Africa and sold for scrap.