South African Cabinet members urged the respondent banks to cooperate with local authorities in the investigation.
Cabinet on Thursday said it will back the Competition Commission's rand manipulation investigation.
This comes after the competition authorities announced that the British multinational Standard Chartered Bank (SCB) admitted liability in the currency manipulation case and agreed to pay a R42 million fine ($2.3 million).
The SCB is one of 28 banks, locally and overseas, currently being investigated for allegations of manipulating the value of the rand exchange rate between 2007 and 2013.
The probe includes fixing bids, bid-offer spreads, the spot exchange rate, and the exchange rate.
Citibank, according to the Commission, already settled the same conduct in 2017.
It is reported that the Competition Commission and the National Treasury of South Africa have updated the Cabinet on the cases currently before courts, as well as concluded settlements with Citibank and Standard Chartered Bank.
"Cabinet supports the important work the Competition Commission is doing in this case. Noting actions in other jurisdictions on the cases involving the ZAR/USD currency trading collusion, Cabinet urges respondent banks currently facing prosecution in our courts to cooperate with local authorities as they did with our foreign counterparts,"
said the Minister in the Presidency, Khumbudzo Ntshavheni.
Last week, South Africa's National Treasury announced increased oversight of OTC derivatives and foreign exchange trading.