(CNN) -- Two South African rugby players were sent home from their national team's tour of Europe on Monday after testing positive for a banned drug.
Mahlatse "Chiliboy" Ralepelle and Bjorn Basson were provisionally suspended from all rugby after the South African Rugby Union was informed of the results late on Sunday.
Winger Basson and forward Ralepelle were found to have used the stimulant methylhexaneamine after being randomly tested following the Springboks' 23-21 win over Ireland on November 6.
"The players have the right to request that their 'B' sample be tested," the SARU said on its website.
"The pair returned an adverse analytical finding for methylhexaneamine, a "non-specified stimulant" on the prohibited substances list of the World Anti-Doping Agency. It is scheduled to be re-classified as a "specified stimulant" from January 1, 2011."
Basson missed Saturday's 34-12 win over Wales with an ankle injury suffered in Dublin and was due to leave the tour anyway.
Ralepelle, who became the first black player to captain South Africa in a warm-up match earlier in the tour, came on the field as a substitute in Cardiff after not being used against Ireland.
They became the latest in a growing list of athletes to test positive for the stimulant methylhexaneamine, which is used in nasal decongestants but has also been an ingredient in now-illegal recreational drugs.
Last year, five Jamaican runners were ruled out of the World Athletics Championships and the World Anti-Doping Agency subsequently added the drug to its 2010 prohibited list.
Two Nigerian sprinters tested positive for it at October's Commonwealth Games in India, with Damola Osayemi losing her gold medal in the women's 100 meters.
Portuguese cyclists Rui Costa and his brother Mario also tested positive that month, while Australia's Daily Telegraph reported that nine sportspeople from that country had done likewise.
South Africa coach Peter de Villiers said his staff were trying to find out what lay behind the positive tests.
"We have to look at what might have caused this and we don't want to put the players at risk. If there is something that we are taking as a squad that might have caused this then we must find that out now," he told the website of South African television channel SuperSport.
"When I informed the two players that they had been tested positive they were both extremely shocked and disappointed. The rest of the team were also gutted when they heard. I was informed of this at 2 a.m. this morning, and now we must follow the correct processes as laid down by the International Rugby Board."
SuperSport reported that Springboks team doctor Craig Roberts said both Ralepelle and Basson had been taking medication for illnesses.
It also said that young South African rugby player Johan Goosen was recently banned for three months after his urine test showed up methylhexaneamine, while