The WBC has provisionally suspended Dillian Whyte’s status as the organisation’s interim world heavyweight champion and mandatory challenger to Deontay Wilder.
Whyte tested positive for a banned substance three days before he beat Oscar Rivas on 20 July.
The Briton, 31, will be allowed to present his case to the WBC.
Whyte has been number-one ranked with the WBC – behind American champion Wilder – for more than 600 days.
He was cleared to take part in the fight with Colombian Rivas – which he won on points – after attending an independent panel hearing.
In a statement on Tuesday, the WBC said: “An “A” sample Ukad collected from Mr Dillian Whyte in relation with his bout against Oscar Rivas yielded an adverse finding.
“In light of that adverse finding, and pending the outcome of the WBC’s own investigation and adjudicatory process, the WBC is provisionally suspending the WBC’s recognition of Dillian Whyte as WBC interim world heavyweight champion and mandatory challenger of the division.
“The WBC has notified Mr Whyte and his team of the WBC’s suspension, and that it will afford Mr Whyte the opportunity to present its position to the WBC at an investigative hearing which will take place at a place and time to be announced in the near future.
“Throughout its investigation and hearing, the WBC will afford Mr Whyte and his team the opportunity to present any available information and materials, and any exculpatory evidence they might deem appropriate.”
UK Anti-Doping (Ukad) has so far declined to comment, while the British Boxing Board of Control underlined its policy of putting its anti-doping procedures, decisions, sanctions and suspensions in the hands of Ukad.
Whyte served a two-year suspension from 2012 to 2014 for unknowingly taking an illegal supplement – and he could face an eight-year ban if he is found to have breached rules again.
It is not known what the banned substance is.
In a tweet, Whyte insisted he beat Rivas “fair and square”, adding that he was “so disappointed with the rubbish that has been said about me”.
Whyte has 26 wins from 27 bouts and became mandatory challenger to WBC heavyweight champion Wilder with victory over Rivas. A bout with Wilder was mandated to take place by 18 May next year.