Brock Lesnar's return to MMA may be short-lived, with the former UFC heavyweight champion facing a two-year ban following a second positive test for a banned substance.
UFC announced on Tuesday that Lesnar's "in-competition sample collection from July 9, 2016, at UFC 200, has tested positive for the same substance as his previously announced out-of-competition collection on June 28, 2016".
Lesnar scored a unanimous decision over Mark Hunt at UFC 200 on July 9, his first UFC fight in four years.
That result is now in question and Hunt thinks he should receive Lesnar's entire $2.5million purse from the fight.
Before UFC hands down any punishment, a full legal review will be conducted.
Lesnar could also face a suspension from WWE, which released a statement on Friday following the announcement of Lesnar's out-of-competition positive test.
Lesnar has not performed with WWE since WrestleMania on April 3 and is not scheduled to return until August 21.
"USADA, the independent administrator of the UFC Anti-Doping Policy, will handle the results management and appropriate adjudication of this case," the UFC statement says.
"It is important to note that, under the UFC Anti-Doping Policy, there is a full fair legal review process that is afforded to all athletes before any sanctions are imposed.
"The Nevada State Athletic Commission also retains jurisdiction over this matter as the sample collection was performed at UFC 200 in Las Vegas.
"Consistent with all previous potential anti-doping violations, additional information will be provided at the appropriate time as the process moves forward."