A second sample from light heavyweight star Sergey Kovalev was flagged for synthetic testosterone, according to BoxingScene's Dan Rafael.
Rafael reported the first positive test stemmed from a sample taken on Dec. 30. Kovalev was tested again Jan. 7, and it had the same outcome.
Rafael noted Kovalev can pay to have his B sample retested.
The 37-year-old could now be facing a lengthy suspension, which would carry significant consequences given his age.
Kovalev hasn't fought since his 11th-round knockout loss to Canelo Alvarez in November 2019. A matchup with Sullivan Barrera was scrapped during the early stages of the COVID-19 pandemic.
The Athletic's Mike Coppinger reported in November that the Russian's deal to fight Alvarez included a pair of DAZN events that would pay out $2.5 million apiece. Lining up the first of those two shows will be tricky in the wake of his positive drug tests.