Johannesburg - Three miners were crushed to death at the Palaborwa Mining Company in Limpopo, the National Union of Mineworkers (NUM) said on Sunday.
NUM's regional secretary in the North East, William Mabapa said the accident occurred at the copper mine on Saturday's night shift.
The miners were investigating a blockage in a rock crusher and were standing beneath it, trying to unblock it.
"When they managed to unblock it, the rocks that were in it fell on them, crushing them to death," he said.
All the men were NUM members.
Mabapa said the department of mineral resources was expected to probe the incident.
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