A WBA spokesman confirmed the organisation had no information on Botha's reported positive test following the fight against Williams in Brisbane, Australia.
The WBA spokesman said the Botha-Williams fight had not been recognised for the organisation's international heavyweight title, due to the organisers' decision to reduce the bout from 12 rounds to 10 at late notice.
The "White Buffalo" appeared to be well ahead on points after 10 rounds, while Williams - the New Zealand heavyweight boxing champion - appeared to be tiring visibly at that point.
Botha claimed he would have achieved a knockout had the fight gone two extra rounds. Instead, he lost via a contentious points decision.
"I have been badgering Williams and his handlers for a rematch," said Botha, who has fought against the likes of Lennox Lewis, Wladimir Klitschko and Mike Tyson during his 61-bout career.