Luis Nery scored a fourth-round knockout to take Shinsuke Yamanaka’s RING and WBC bantamweight titles last month, but the reign will be short-lived.

A pre-fight sample submitted by Nery (24-0, 18 knockouts) tested positive for the banned substance Zilpaterol, after which he had the right to have his “B” sample test. That sample also came back dirty, sources told RingTV.com.

Nery was tested by the Voluntary Anti-Doping Association, which works in conjunction with the WBC Clean Boxing Program.

WBC Pesident Mauricio Sulaiman told RingTV.com he expects to have an official ruling on the matter later this week.

It’s possible Nery ingested contaminated meat. Zilpaterol is an adrenergic agonist (stimulant) similar to Clenbuterol and is often used to increase the size of cattle. When used by athletes, the substance is believed to help the development of muscle and also increases the metabolism.

As a result of Nery’s “B” sample result, Yamanaka will be reinstated as RING bantamweight champion. And in accordance with THE RING’s policy on performance-enhancing drugs, Nery, who was rated in Top 10 prior to the bout, will exit the ratings entirely.

The 22-year-old Mexican “will have the opportunity to earn his way back into the ratings after any suspension period is completed,” per THE RING’s rules.

Yamanaka (27-1-2, 19 KOs) made 12 successful defenses of the WBC title he won in 2011. All of the Tokyo-based fighter’s bouts have been in Japan, where he’s a star. The 34-year-old was in THE RING’s pound-for-pound Top 10 prior to the knockout loss, which now figures to be overturned by the commission in Japan.

Yamanaka will not re-enter the pound-for-pound Top 10 because the Editorial Board feels other fighters have surpassed him.

Mike Coppinger is the Senior Writer for RingTV.com. Follow him on Twitter: @MikeCoppinger