Boxing South Africa (BSA) confirmed that Buthelezi, 24, collapsed towards the end of the fight on June 5 before being rushed to hospital.
A video posted on social media appeared to show Buthelezi fighting in the direction of an empty corner of the ring, seemingly confused, prompting the referee to end the fight.
In a statement, Boxing South Africa said it “will conduct an independent medical review of the injury and will then make public the results of that medical review.”
“Boxing South Africa and the Buthelezi family wishes to request members of the public and the media to give them space while mourning the passing away of this great boxer who was exemplary both outside and inside the ring,” it added.
Studies show that traumatic brain injuries are common among both professional and amateur boxers. In a 2020 statement, the World Medical Association said that “boxing is qualitatively different from other sports because of the injuries it causes and that it should be banned.”