Nearly 500 miners who were trapped underground by a fire at a gold mine in South Africa on Sunday were brought to the surface safely, a spokeswoman for mining company Harmony Gold said.

The fire at the mine near Carletonville, about an hour from Johannesburg, was detected at around 0740 GMT, nearly two kilometres (1.25 miles) underground.

"All the miners are out," Charmane Russell told AFP. "Fortunately in this instance, things went according to plan."

Harmony Gold said 486 miners were working in the Kusasalethu mine when the fire broke out.

All employees were notified and advised to move to refuge bays in the mine, said Russell.

"Our employees have been trained for this," she said.

Mining operations were suspended as rescue teams were brought in to contain the fire, cutting off ventilation to the flames before moving from level to level to locate the workers.

By late Sunday, the fire had been contained and hundreds of miners had been brought to the surface.

But 18 remained missing.

South Africa's President Jacob Zuma expressed shock at the incident, wishing "the miners and their families strength" and urging "everything possible" be done to rescue them.

"I urge all South Africans to keep the miners in their thoughts and prayers during this difficult period," he said in a statement.

Less than an hour later, the missing men were reported as safe, rescued from nearly 3.5 kilometres (2.17 miles) underground, Russell said.

No injuries were reported.

"We are extremely grateful that all of our colleagues have been brought to surface, without injury," Harmony Gold CEO Graham Briggs said in a statement.

He said the cause of the fire would be investigated, but an earlier company statement said it was believed to have started while maintenance work was being done on an air cooler.

South Africa's economy is heavily dependent on the mining of platinum, gold and coal.

According to industry lobby group This Is Gold, the country was listed as the sixth largest gold producer in 2013, exporting 168.8 tonnes of the mineral. The gold sector employed around 132,000 people that year.

South Africa's gold mining industry is worth $4 billion and its mines are among the deepest in the world, accounting for nearly half of all gold reserves, according to South Africa's Chamber of Mines.

But accidents are commonplace.

In February 2014, over 200 workers were feared trapped after a rock fall inside an illegal gold mine dug behind a cricket stadium east of Johannesburg.

Just two weeks earlier, nine miners died after an earth tremor sparked an underground blaze at another Harmony Gold mine west of Johannesburg.

In July 2009, nine workers were killed in a rock fall in a platinum mine.

The same year, at least 82 people digging illegally in an disused gold mine shaft died when a fire broke out underground.