Correctional Services spokesman Manelisi Wolela has denied allegations that student leader Mcebo Dla.
SA's business hub has made it into an index that lists the world's top 50 centres of commerce.
The MasterCard Worldwide Centres of Commerce Index put Joburg 47th, the only African city in the index's top 50 cities to do business in.
Johannesburg beat Sao Paulo, Warsaw and Moscow.
London, New York, Tokyo, Chicago, Hong Kong, Singapore, Frankfurt, Paris, Seoul and Los Angeles were the top 10 cities. - Xolile Bhengu