The search is still continuing for the three mine workers who have been trapped underground at Lily Mine in Louisville, outside Barberton, since Friday last week.
John Sibiya, the Mpumalanga secretary for the Association for Mineworkers and Construction Union, said there had been no new developments since rescue teams found a tyre near the container.
"I don't want to lie to you, the search continues. The big challenges are the big rocks that build up every time we make a blast. The more we try to blast those rocks, the rocks on the surface pile up below. It's just a never-ending mission," Sibiya said.
Sibiya told News24 on Thursday that the tyre provided a glimmer of hope of finding the three, but there were still rocks blocking the way.
New technology is being used to loosen a huge rock weighing between 20 tons and 30 tons that is hampering the rescue mission.
Yvonne Mnisi, Pretty Mabuza and Solomon Nyarenda were in a lamp room that was housed in a container near the entrance to the mine when a central pillar of ore, called a crown pillar, collapsed last Friday. The container was swallowed up in a sinkhole as big as a rugby field.
Seventy-six miners were rescued after the collapse.
Mineral Resources Minister Mosebenzi Zwane said he would return to the mine on Saturday to get a progress report on the rescue operation.