Claressa Shields is under investigation after testing positive for marijuana following her win over heavyweight Danielle Perkins in Michigan earlier this month.
The 29-year-old, who is a three-weight undisputed champion, has been suspended form fighting in the state by the Michigan Unarmed Combat Commission.
Shields tested positive after providing an “oral fluid sample” after the fight oin February 3.
Marijuana is banned in-competition by the World Anti-Doping Agency (Wada).
The WBO, a sanctioning body without the power to suspend boxers, has asked Shields to explain herself, while the Michigan Commission investigates possible disciplinary action.
“Ms Shields’ conduct as a licensed professional boxer constitutes an imminent threat to the integrity of professional boxing, the public interest, and the welfare and safety of professional athletes,” the Michigan Commission said.
Shields addressed rumours of a failed drugs test last week, insisting that she was a “clean athlete”.
The Michigan-born fighter won Olympic gold at 17 and has won titles in multiple weight classes as a pro.
She is undefeated in 16 fights and the first boxer, male or female, to win undisputed titles in three weight classes in the four-belt era.
