Mexican boxer Luis Nery, who denied Shinsuke Yamanaka a 13th straight defense of his WBC bantamweight title last week, failed a drug test performed in the lead-up to the fight, the World Boxing Council said Wednesday.

"The WBC has been notified by VADA (Voluntary Anti-Doping Association) of an adverse finding from an out of competition sample taken from WBC bantamweight champion Luis Nery," the body said on its official website.

"The substance is zilpaterol which is very similar to clembuterol (sic). The adverse finding came from the testing leading to his world title fight versus Shinsuke Yamanaka which took place in Japan on August 15," it said.

The Japan Boxing Commission said they have been contacted by the WBC and are awaiting test results from the "B" sample and post-fight sample before moving forward with further discussions.

Nery, a 22-year-old top-ranked challenger, improved his record to 24-0 when he defeated previously fellow unbeaten fighter Yamanaka in a fourth-round technical knockout at Shimadzu Arena Kyoto.

With a 13th straight title, Yamanaka had been hoping to equal a Japanese record for most consecutive defenses set by former WBA light flyweight champion Yoko Gushiken in 1980.