The South African city of Johannesburg was built on enormous gold reef. Today, many of the mines have closed, but criminal gangs continue to work the disused and abandoned tunnels.

It is dangerous and often deadly, and as well as digging in the disused mines, heavily armed gangs also steal gold from the remaining working shafts.

The decline of the gold mining sector, unemployment, illegal migration, and poverty have all contributed to the growth of this criminal activity.

Nomsa Maseko investigates.