Harmony Gold Mining Co. announced that eight workers died and one was still missing following a rockfall at its Doornkop Mine in South Africa.

The rockfall is believed to have triggered a fire on Feb. 4 in the gold mine more than one-mile underground.

“The search continues for the ninth employee,” the Johannesburg-based company said in a statement on Feb. 6. Operations at the mine west of the city are suspended.

Search and rescue and deep-level firefighting teams were deployed at about 6 pm on Feb. 4 after the fire broke out 1,733 m (5,700 ft) below the surface, according to the company. Eight trapped miners were found in a refuge chamber and brought out unharmed.

The fire started when a tremor with a magnitude of 2.4 caused a rock fall that damaged power cables, according to the National Union of Mineworkers, which said ventilation and water pipes were also affected.

There were 112 deaths in the country’s mining industry in 2012, according to the Chamber of Mines.

“There’s nothing about a seismic event that one can really do,” Franz Stehring, head of mining at the union Uasa told Bloomberg. Investigators will be checking whether the workers had their rescue packs, which supply enough oxygen for 60 minutes, whether the rescue bays work and whether the workers knew where to find the refuges, he said.

The Doornkop incident is the worst in the local industry since nine miners died after the cable of a shaft elevator snapped on May 1, 2008, at Gold Fields Ltd.’s South Deep mine.

Mines Minister Susan Shabangu promised “thorough investigations” of the incident as she spoke at a press conference at the mine, along with Harmony Chairman Patrice Motsepe.

Doornkop, about 30 km (19 miles) from Johannesburg, produced 3,631 kg of gold in 2013, according to Harmony’s website. The single-shaft mine at a depth of just under 2,000 m accounts for about 10 percent of the company’s South African production. There were two fatalities at Doornkop in 2012 and none last year.