Johannesburg. Rescue workers at a South African gold mine say they have recovered eight bodies after a fire and rock fall.

One other miner remains missing at the Doornkop mine west of Johannesburg, the government said.

Earlier, eight other miners were found unharmed in an underground refuge chamber and brought to the surface, mine owners Harmony Gold said.

The fire began on Tuesday evening about 1,700m (5,600ft) below ground. The cause of the blaze is not yet clear.

"The situation is deeply regrettable,” Mineral Resources Minister Susan Shabangu said in a statement.

"We must ensure that we do all we can to get to the bottom of what caused this incident in order to prevent similar occurrences in future.” Eric Gcilitshana of the National Union of Mineworkers (NUM) said the bodies had been discovered on Wednesday evening.

"This is a very sad moment for us in the NUM. Our hearts go out to the families of the deceased,” he was quoted as saying in The Star newspaper. Mine officials said earlier that the rescuers had been struggling to access the affected area because of smoke and falling rocks.

Although the cause of the tragedy has not been established, the NUM has suggested that an earth tremor caused a rock fall which triggered the fire.

Harmony Gold has confirmed there was some seismic activity in the area.

The NUM has called for an urgent investigation into the incident.

Correspondents say it is the most serious accident in South Africa’s mines since nine workers were killed in a rock fall at a platinum mine in July 2009.

South Africa has some of the world’s deepest gold mines and safety is a major issue, not least because thousands of illegal miners also operate in the same areas, says the BBC’s Andrew Harding in Johannesburg.

Mining is a vital part of the South African economy but the industry has been hit by a series of violent strikes in recent years.

Talks to end a two-week strike at the world’s top three platinum producing mines collapsed on Wednesday.

AngloAmerican Platinum, Impala Platinum and Lonmin have been negotiating with the Association of Mine and Construction Workers Union (Amcu), a rival to the NUM.

The mineworkers are calling for an end to what they call the "apartheid wage structure” and want their pay to be doubled.

But mine bosses have said they cannot afford such steep increases.

South Africa holds about 80% of the world’s known platinum reserves and is the fourth-biggest gold exporter.