Flagged by USADA, Francisco Rivera says he might have eaten tainted meat in Mexico

Francisco Rivera is in hot water with USADA, but poised to present a compelling defense.

The UFC bantamweight was flagged by the agency for a potential anti-doping violation, the UFC announced Wednesday on its website. The statement said the potential violation is in relation to a July 23 out-of-competition sample taken from Rivera.

Rivera told MMA Fighting on Wednesday night in a statement through his Iridium Sports management group that he was told by USADA that he tested positive for clenbuterol.

Rivera, 34, said he was vacationing in Mexico just before the drug test, which is significant in this case. The World Anti-Doping Agency (WADA) issued a warning in 2011 that said China and Mexico have a "serious problem" with meat contaminated with clenbuterol, which is clinically used in some countries to treat breathing disorders in humans. Rivera said he ate meat on multiple occasions when he was in Mexico.

Last week, USADA announced that UFC fighter Ning Guangyou of China tested positive for clenbuterol, but did not receive any sanction. USADA said it determined after reviewing Guangyou's whereabouts, dietary habits and lab reports (it was a trace amount of the substance) that he had likely ingested the banned agent in tainted meat. The UFC is allowing Guangyou's fight against Marlon Vera at UFC on FOX 21 next week to go on.

Rivera said he plans on putting forth a similar defense. He added that he passed every other USADA drug test this year. The USADA website shows he was tested twice before July 23.

The California native maintains that he did not knowingly consume any prohibited drugs. If USADA determines that he did knowingly take it, Rivera is facing a two-year suspension.

USADA was not immediately available to comment for this story as of Wednesday night.

Rivera (11-7, 1 NC) fought Erik Perez at UFC 201 on July 30 — after the drug test was taken, but before the results came back — and lost via unanimous decision. The 135-pound slugger has now dropped three straight, though his split-decision loss to Brad Pickett in January was heavily in dispute.

"Cisco" also tested positive for a banned substance in 2012, when he failed a drug test in relation to UFC 149 for ephedra. Rivera was suspended 90 days and his win over Roland Delorme was overturned to a no-contest.