Botha, who lost a controversial fight to former All Black rugby star Sonny Bill Williams in Brisbane on Friday, reportedly failed a drugs test on the eve of the fight.
Results of a urine sample submitted by Botha in Brisbane last Tuesday under WBA regulations show he had Phentermine - a banned stimulant - in his system.
GALLERY: Sonny Bill Williams v Francois Botha
VIDEO: Sonny Bill Williams v Francois Botha - highlights
The drugs test, which has now been forwarded to the WBA's global headquarters in Panama, also detected Benzodiazepine, which suggested Botha was also using a valium-type product.
The fight was marred in controversy when it ended with Williams receiving a unanimous points decision. But the fight ended after 10 rounds, instead of 12, as per WBA rules and as had been advertised.
Botha was furious with officials after the decision was made to shorten the bout, with the 44-year-old looking to have worn out Williams by the end of the 10th."You know I love Sonny Bill, I think he's a great guy, a gentleman, but this was bullshit," the 115kg "White Buffalo" said in an interview after the fight.
"If you look at the crowd, you know who won. You've got to win fair and square, not with the advantage of the judges, you've got to fight. According to me I won, hands-free."
Botha also said he wanted a rematch against the New Zealand heavyweight champion.
"A rematch - if he can beat me he can go on, but if he doesn't he should throw in the towel."