UK Anti-Doping has launched an investigation into Conor Benn's failed drugs test that led to the postponement of his grudge match against Chris Eubank Jr last week.
The catchweight fight at London's O2 arena, due to take place on October 8, was called off after it was revealed that last month Benn had tested positive for trace amounts of fertility drug clomiphene, which elevates testosterone levels in men.
Benn, who has not been suspended, returned the positive result in a test conducted by the Voluntary Anti-Doping Association (VADA), prompting the British Boxing Board of Control (BBBofC) to declare the fight "prohibited" and "not in the interests of boxing".
The board has now said UKAD is looking into the failed test.
A statement said: "UK Anti-Doping (UKAD) has launched an investigation in relation to Mr Benn and the board is in communication with UKAD in relation to that investigation. The board will release further details in relation to this matter, as and when appropriate."
In a statement last week, Benn said he was "completely shocked and surprised" by his positive test, adding his "immediate focus is on clearing my name because I am a clean athlete".
The bout was intended to be a continuation of the Benn v Eubank feud in which the rivals' fathers battled it out in two ferocious contests in the early 1990s.
A catchweight of 71.2 kilograms was agreed for the sons to continue the family feud into a trilogy fight, meaning Benn would have to move up two weight divisions and Eubank lose three pounds.