( CNN ) -- At least nine miners remain trapped in a South African gold mine after an underground fire , the Harmony Gold mining company said Wednesday . South African emergency workers rescued eight other miners and brought them to the surface at the Doornkop mine , west of Johannesburg . `` Rescue teams continue the search for the remaining nine miners who are still unaccounted for , '' the company said in a prepared statement . `` The underground fire has been subdued , although conditions underground remain challenging . '' It said the eight miners who were rescued were unharmed but would be kept under medical observation during the night as a precaution . The fire is reported to have broken out about 1,733 meters ( 5,700 feet ) underground around 6 p.m. local time Tuesday . Harmony Gold spokesman James Duncan said seismic activity -- a magnitude-2.4 tremor that caused rock to fall -- may have caused the fire . `` The rock fell , damaged a cable , which we think caused a spark which then ignited something and caused the fire , '' he said . `` Obviously , this is all subject to inquiry . Our priority is finding the missing men . '' All operations other than essential services at the mine have been suspended . CNN 's Marie-Louise Gumuchian and Nana Karikari-apau contributed to this report .
NEW : Underground fire has been subdued , but conditions remain challenging , he says . Eight other miners killed earlier are unharmed . Rescue operations continue at Doornkop mine , west of Johannesburg . The fire is believed to have broken out more than a kilometre underground .