Ryan Garcia tested positive for the performance-enhancing anabolic agent ostarine on the day before and the day after his surprise win over Devin Haney last month in New York City, according to a Voluntary Anti-Doping Association (Vada) letter sent to both parties.

ESPN was first to report the news of Garcia’s failed drug tests, which if confirmed would likely result in a suspension and the overturning of the result to a no-contest.

Garcia has 10 days to request that his B-sample be tested. Garcia’s A-sample also reportedly screened positive for 19-norandrosterone, though its presence is being confirmed by carbon isotope ratio testing.

Ostarine is an anabolic agent regarded as a safer alternative to steroids which appears on the World Anti-Doping Agency’s 2024 Prohibited List.

Garcia vehemently denied taking any illegal substances in a video posted to X on Wednesday night.

“Everybody knows that I don’t cheat,” Garcia said. “I’ve never taken a steroid in my life. I don’t even know where to get steroids, at the end of the day. I barely take supplements ... Big lies, I beat his ass.”

The 25-year-old Garcia scored three knockdowns of Haney and handed the WBC super lightweight champion the first defeat of his professional career in a dramatic upset on 20 April.

The scheduled 12-round encounter at Brooklyn’s Barclays Center had been downgraded to a non-title bout when Garcia weighed in at 143.2lbs – 3.2lbs above the division limit – creating a situation where Garcia could no longer take Haney’s championship, only his unblemished professional record.

“We learned about this situation not too long ago and it’s unfortunate Ryan cheated and disrespected both the fans and the sport of boxing by fighting dirty and breaking positive not once, but twice,” Haney said in a statement to ESPN.

“Ryan owes the fans an apology, and by his recent tweet he still thinks this is a joke. We put our lives on the line to entertain people for a living. You don’t play boxing. This puts the fight in a completely different light. Despite the disadvantage, I still fought on my shield and got back up! People die in this sport. This isn’t a joking matter.”

Ostarine is a selective androgen receptor modulator that has been on Wada’s banned list since 2008. Amir Khan was hit with a ban from all sport for two years after he was found guilty of having it in his system on the night of his 2022 fight with Kell Brook.