Nearly 80 rescued miners were brought to the surface on Friday, police said, after about 115 were trapped underground following a collapse at a gold mine in northeastern South Africa earlier in the day.

Mike McChesney, chief executive of the small gold producer Vantage Goldfields told Reuters that 115 workers had initially been trapped at Lily mine, but most had been rescued and the rest would probably emerge soon.

"As we speak they might already all be out. Most have been evacuated," he told Reuters by telephone from the company's offices in Barbeton town in Mpumalanga province about 360 km east of Johannesburg. No fatalities have been reported.

South Africa's mines are the deepest and among the most dangerous in the world. Fatalities in the industry have been falling due to both improved safety practices and a reduction in the labour force as production declines.

The collapse occurred at the main entrance to the mine, the company said in a statement.

Vantage Goldfields is an Australia-based company mining gold at Barberton, a town that traces its origin in the country's 19th century gold rush. Vantage was delisted from the Australian bourse in January 2015.

Manzini Zungu, spokesman for the Association of Mineworkers and Construction Union (AMCU), said some 115 union members were trapped underground after a cave-in at the mine also known as Makonjwaan.

"At this point, it's unclear what caused the disaster," he said.

Some 76 mine workers had been brought to the surface so far and another 42 people were still unaccounted for, police spokesman Selvy Mohlala said.

Last year, 77 workers were killed in mining accidents, the lowest number on record.