Correctional Services spokesman Manelisi Wolela has denied allegations that student leader Mcebo Dla.
Genetic modification has been available in South Africa for 10 years and is targeted at small-scale black farmers because of its high-yield properties.
It is common in mielies, cotton and soya beans. A genetically modified (GM) mielie seed with a built-in pesticide called Bt maize is used in SA.
Soya is used in products such as soups, sauces and breakfast cereals. It also increases the protein content of processed meat products and replaces meat in vegetarian foods.
Environmental groups have however warned that the "guaranteed high yields" reported by farmers who use Bt could be drastically reduced in a few years because the pests would gradually become resistant to the in-built pesticide.
Vanessa Black, an anti-GM campaigner at EarthLife, said: "This would mean that the companies that manufacture these products would have to come up with new pesticides. This would also increase the use of pesticides, which is detrimental to the environment."
Black warned that the use of Bt was not sustainable in the long term because farmers would be forced to buy seeds every planting season from a single supplier. She said its prolonged use eroded the quality of soil.
Black said it was disconcerting that South African legislation did not force manufacturers to declare food products as genetically modified unless they contained "genes from animals or humans and if it would have to be cooked differently" because of its nature.
Haidee Swanby of the African Centre for Biosafety said the technology was meant for large-scale commercial farmers in developed countries and not small-scale farmers.
"The technology would result in massive job losses, especially in rural areas, at a time when we cannot afford it and encourage more migration to big cities," said Swanby.
"Organic farming is better because it allows people to grow more diverse crops to cater for the nutritional needs of the local population.''