The South African Rugby Union have announced that the 'B' samples of Bjorn Basson and Chiliboy Ralepelle confirm their positive tests for a banned substance.
The Springbok duo both failed drugs tests for methylhexaneamine after South Africa's victory over Ireland on November 6.
Winger Basson and hooker Ralepelle were sent home from the northern hemisphere tour while their 'B' samples were analysed. The initial findings have now been confirmed.
Neither player has opted to appeal the testing procedure, with both now facing the possibility of doping bans.
The SARU will set up a tribunal to investigate the positive tests, which the Springboks claimed could have been triggered by a nutritional supplement.
"The South African Rugby Union (SARU) will appoint an Anti-Doping Tribunal to investigate an allegation of an anti-doping offence committed by Chiliboy Ralepelle and Bjorn Basson," a SARU statement read.
"The players returned an adverse analytical finding for a prohibited stimulant, methylhexaneamine, following the match between South Africa and Ireland in Dublin on 6 November 2011.
"Both players asked for their 'B' sample to be tested, which confirmed the findings of the 'A' sample.
"The players will not contest the testing procedures or related matters under the 2010 Autumn Internationals Anti-Doping Programme and therefore the investigation and hearing will be conducted in South Africa.
"Investigations remain ongoing and a date for the hearing, as well as the composition of the tribunal, will be announced once those have been completed in the new year."
Ralepelle and Basson have maintained their innocence while South Africa have scaled back their use of supplements, which are likely to be reviewed during the SARU probe.