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.
The WBC, which sanctioned the bout, said it received no notification of the positive test.
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.