Alexander Povetkin's B sample has tested positive for Ostarine ©Getty Images

Russian boxer Alexander Povetkin’s second doping sample has produced "controversial results" according to a promoter - who said he was told the tests were "clean".

Andrei Ryabinsky, the director of World of Boxing, spoke to TASS after a laboratory in Lausanne said today that the Athens 2004 Olympic super-heavyweight champion’s B sample tested positive for Ostarine.

This matches the results from his original sample with both examinations being conducted by the Voluntary Anti-Doping Association.

However, the boxer's promoter Ryabinsky said: "We have the results of alternative tests from another laboratory, the one in Lausanne.

"The probe samples are clean."

Alexander Povetkin won super-heavyweight gold at the 2004 Olympic Games in Athens ©Getty Images
Alexander Povetkin won super-heavyweight gold at the 2004 Olympic Games in Athens ©Getty Images

He added another independent examination should be required.

The World Boxing Council (WBC) refused to approve a fight between Povetkin and Canadian Bermane Stiverne on December 6 after the Russian tested positive for Ostarine, also known as MK-2866, which helps an athlete’s endurance.

However, samples from December 13 and 15 came back negative with Ryabinsky saying the drug takes more than 12 months to leave the human body and that he thinks Povetkin may have taken the banned substances unknowingly.

In December, Ryabinsky made similar claims when discussing the samples after the bout which was for the vacant WBC heavyweight title.