By Jim Edwards

Brock Lesnar's triumphant return to the UFC could be in serious trouble.

It was reported on Friday evening by Brett Okamoto of ESPN that the UFC have been notified of a potential anti-doping violation by Brock Lesnar from a test stemming back to June 28.

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Lesnar competed last weekend at UFC 200 on July 9th where he defeated Mark Hunt via a unanimous decision. In the build-up to the fight, Hunt made several accusations that Lesnar was 'juiced to gills', though Lesnar refuted his accusations several times and on the UFC 200 media conference call said, "I'm white and I'm jacked, deal with it."

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Lesnar was put on the USADA program shortly after it was announced that he would return at the beginning of June. He was then tested five times during the first two weeks of him being on the program though it is understood that the test he has been cited for took place after that.

In an official statement released by the UFC, the promotion said USADA received the testing results July 14. The sample was tested at UCLA Olympic Analytical Laboratory, a WADA-accredited lab. USADA, as is its policy, did not release the name of the substance Lesnar tested positive for.