Boxer Ryan Garcia has tested positive for the prohibited substance ostarine, according to official sources.

Star boxer Ryan Garcia tested positive for the performance-enhancing substance ostarine both the day before and the day of his stunning victory over Devin Haney last month, according to a letter from the Voluntary Anti-Doping Association (VADA) sent to involved parties and obtained by ESPN.

The urine samples, collected before the fight, revealed the results only after the event had concluded.

Garcia now has 10 days to request the testing of his B-sample. Additionally, Garcia's A-sample tested positive for 19-norandrosterone, although confirmation is pending further analysis.

"Everybody knows that I don't cheat," Garcia stated in a video posted on X. "I've never taken a steroid. I don’t even know where to get steroids. I barely take supplements. Big lies, I beat his ass."

Golden Boy Promotions, led by Oscar De La Hoya and representing Garcia, said in a statement that it is collaborating with Garcia's team to "determine how this finding came to be."

"Ryan has issued multiple statements denying any knowing use of banned substances—and we believe him," the statement from Golden Boy Promotions added.

The controversy casts a shadow over Garcia's majority decision victory, which now risks being overturned unless the B-sample tests negative—a rare occurrence. Despite failing to make the weight at 143.2 pounds for the WBC 140-pound title fight, leading to a penalty fee paid to Haney of over $600,000, Garcia's performance had been formidable, flooring Haney three times.

Even though Haney remained the junior welterweight champion post-defeat, he slipped in the rankings from No. 2 to No. 4 in ESPN’s 140-pound list and lost his pound-for-pound recognition.

The New York State Athletic Commission emphasized the importance of "safety, fairness, and integrity in professional athletic competition" and confirmed their ongoing review of the matter in coordination with VADA.

Ostarine, known for its capability to boost muscle growth, stamina, and recovery, has been banned by the World Anti-Doping Agency since 2008 and classified as an anabolic agent in 2022.

Previously, boxer Lucian Bute tested positive for ostarine in 2016 following his fight with Badou Jack, and Amir Khan received a two-year suspension from UK Anti-Doping after testing positive for the substance in 2022.

Despite the adverse findings, Garcia's upset win marked a significant highlight in his career, which boasts a vast social media following and an impressive track record in the ring.