Brock Lesnar is facing a USADA anti-doping violation after testing positive for a banned substance in a June 28 drug test. Lesnar, though, also came back clean in multiple previous tests, MMA Fighting confirmed Friday night with USADA.

"We'll get to the bottom of this," Lesnar said in a statement to The Associated Press.

Lesnar provided the AP with copies of three letters notifying him that he had passed USADA drug tests prior to UFC 200. Lesnar was tested eight times in the month leading up to his fight with Mark Hunt — five of them in the first two weeks he was under the UFC's anti-doping policy.

USADA spokesperson Ryan Madden confirmed with MMA Fighting that Lesnar passed multiple tests before the June 28 sample came back positive for a prohibited agent.

"With Mr. Lesnar having spoken publicly about the issue, I can confirm that he has been notified of a potential anti-doping policy violation, stemming from an out-of-competition sample collection on June 28, 2016," Madden said in a statement. "I can also confirm that the results from his previous samples collected by USADA were all reported as negative. Although USADA will not be providing any further specifics of the case at this time, I can tell you that Mr. Lesnar, as with every athlete under the UFC anti-doping policy, will be provided full due process under the rules."

The UFC announced Lesnar's potential anti-doping violation Friday. USADA got the results back from the lab Thursday night. Because the results had yet to come back in time, Lesnar was still allowed to fight Hunt at UFC 200 on July 9 in Las Vegas. Lesnar defeated Hunt by unanimous decision. That result could be overturned by the Nevada Athletic Commission, which also retains jurisdiction in this case because of the sample collection's proximity to the fight.

Lesnar, 39, will get a full adjudication process and chance to clear his name with USADA. He could be facing a two-year suspension from the UFC's anti-doping partner plus further sanctions from the NAC.

USADA does not release the name of the substance an athlete tests positive for until the completion of the adjudication process or the athlete makes it public first.

Lesnar was making his return to the UFC after nearly five years at UFC 200. His return drew controversy when the UFC waived its rule that states retired fighters must inform USADA four months out of their return fight so they can be placed into the drug-testing pool.