By Igor Lazorin, tass

As previously reported on BoxingScene.com, Deontay Wilder's defense of the WBC heavyweight title against Alexander Povetkin has been postponed by the sanctioning body after the Russian challenger failed a drugs test.

'Keeping the priority of safety and also the principle of justice, the WBC will continue the investigation into the case,' the WBC said in a statement. 'Consequently, the event scheduled for May 21 in Moscow is hereby officially postponed.'

It added that 'the WBC will be releasing more information in the coming days regarding the final ruling on the matter.'

Povetkin's promoter has said the substance found in an April test was meldonium, the stamina booster for which tennis star Maria Sharapova and dozens of other athletes in ex-Soviet nations have tested positive since it was banned from January 1.

Wilder, an unbeaten American (36-0), had been due to make his fourth defence of the belt he won against Bermane Stiverne in January last year. For Povetkin (30-1), it is his first world title challenge since dropping a unanimous decision to Wladimir Klitschko in 2013.

Wilder had made allegations against Povetkin in an interview last year with BoxingScene. Wilder said he believed the Russian to be 'on some kind of steroids' but said he was still willing to fight him.

Povetkin's promoter Andrei Ryabinsky told Russia's Tass news agency on Friday that his fighter had tested positive in April, but that only 'leftover traces of meldonium at a very low concentration were found.'

These traces, Ryabinsky said, were the result of Povetkin taking meldonium in September last year before it was banned.

But Ryabinsky's version of the details have been contradicted by the Las Vegas-based Voluntary Anti-Doping Association [VADA], who handled the random drug testing protocol with the WBC.

According to information from VADA, Povetkin tested negative for meldonium on April 7, April 8 and April 11, and only tested positive on April 27 - which indicates he ingested the drug somewhere between April 11th and April 27th.

Wilder's trainer and co-manager is stunned by the news.

"[Povetkin] lied to us," said Wilder trainer and manager Jay Deas. "We are devastated. We were preparing for this fight for a long time. It's a big disappointment for a lot of people. I don't have any other words."

Athletes in several sports have avoided suspensions for meldonium positive tests under new World Anti-Doping Agency guidance issued in April - if the concentration of the heart drug is low enough to indicate they did not take it after Jan. 1.

Ryabinsky indicates that his boxer will not be punished with a suspension. He scheduled a press conference tomorrow to discuss the situation with the local media.

"Alexander will not be punished. Only his fight with Wilder will be postponed," Ryabinsky said.