Marijuana didn't show up in Nate Diaz's system, but that doesn't necessarily mean he won't be sanctioned.

Diaz passed his UFC 202 fight-night drug test administered by USADA, UFC vice president of athlete health and performance Jeff Novitzky told MMA Fighting on Monday night. However, USADA is still reviewing Diaz's use of a cannabidiol (CBD) oil vape pen at the post-fight press conference that night, per spokesperson Ryan Madden.

Though Diaz's drug test was clean, him telling the media he was vaping a CBD oil pen could fall under the "admitted use" clause in the UFC's anti-doping policy run by USADA.

Cannabinoids are only banned by the WADA Code in-competition, but that definition includes the six hours before and after a fight. The UFC 202 press conference was within that window. Cannabidiol is one of 113 active cannabinoids contained in cannabis.

"It's CBD," Diaz said at the presser following his majority decision loss to Conor McGregor on Aug. 20. "It helps with the healing process and inflammation, stuff like that. So you want to get these for before and after the fights, training. It'll make your life a better place."

Madden told MMA Fighting two days after the fight that the situation was under review.

"I can confirm that USADA is aware of the situation and is currently gathering information in order to determine the next appropriate steps," Madden said at the time.

That process remains ongoing, Madden said.

Nevada Athletic Commission (NAC) executive director Bob Bennett told MMA Fighting's Ariel Helwani last week that the commission would not be pursuing any disciplinary action against Diaz, because the NAC has a different definition of in-competition. That window in Nevada ends essentially after the post-fight drug test is complete.

All the other UFC 202 fight-night drug tests also came back negative, Novitzky said. McGregor beat Diaz in the main event and Anthony Johnson knocked out Glover Teixeira in the co-headliner.

Cannabis is considered a "specified substance" by the UFC anti-doping policy. It's not an anabolic steroid or hormonal agent, but it is still prohibited in certain cases, like in-competition. An athlete violating the policy for a specified substance can face anywhere between a public warning to a suspension of up to one year from USADA.

CBD has been used to treat epilepsy and schizophrenia. Studies have shown that it has fewer side effects than THC and does not cause any psychoactivity.