Former world champion Parker tested positive as part of a anti-doping examination conducted the same day he faced 11th-round stoppage to British heavyweight Ipswich-born Wardley.
Fabio Wardley together with Joseph Parker were part of a pulsating contest staged in the UK capital on 25 October to establish who would become next in line for the WBO against undisputed world heavyweight champion Ukrainian champion Usyk.
Parker was previously the primary candidate to face Oleksandr Usyk subsequent to putting together a notable six consecutive victories, but put his contender position on the line in London and suffered a stoppage in round eleven.
A standard screening conducted on Joseph Parker by Vada the day of the match returned positive and leaves the 36-year-old facing a challenge to demonstrate his cleanliness.
The boxer's representatives released a communique stating: "Vada informed everyone involved that Joseph Parker returned an adverse finding after a doping test administered on the fight day. As the investigation continues, no further statements are forthcoming for now."
Joseph Parker became world champion six years ago until he surrendered the WBO title through a points decision against Anthony Joshua in Wales two years later.
The fighter became a frequent visitor across the United Kingdom after that, having eight matches overall in the UK and relocating to the Irish capital for preparation under highly regarded trainer former champion Lee over the past few years.
Under the tutelage of Lee, Parker overcame the 2022 setback against Joe Joyce to secure several successes positioning him at the front of the line to face Usyk until he suffered defeat against Wardley.
Subsequent to the boxer produced a failed test when he fought Wardley, reportedly involving cocaine, a probe regarding the results has been started.
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