UFC light heavyweight Chael Sonnen has failed a random drug test in the state of Nevada and will not fight Vitor Belfort at UFC 175 on July 5.
The Nevada State Athletic Commission randomly tested Sonnen last month while he was in Las Vegas to attend a UFC news conference. Results confirmed the presence of two illegal substances, Anastrozole and Clomiphene.
NSAC chairman Francisco Aguilar confirmed the test results to ESPN.com on Tuesday.
UFC officials also acknowledged the situation.
"UFC officials acknowledge irregularities in a recent random test," the promotion stated. "Chael is planning on addressing the matter this afternoon."
Sonnen (28-14-1) is expected to discuss the test results on Fox, where he serves as a UFC analyst. The substances Sonnen tested postive for are classified as anti-estrogenic.
Anastrozole is used to treat early stages of breast cancer. Clomiphene is used in cases of female infertility.
Sonnen will likely face a suspension in the wake of the test. Sources indicate to ESPN.com he will not file an appeal.
Sonnen, 37, has stated he was diagnosed with hypogonadism in 2008, resulting in a low level of testosterone. He had been approved the use of testosterone-replacement-therapy (TRT) in his last six fights, twice in Nevada.
The NSAC banned TRT in combat sports in February, however, which forced Sonnen to abandon treatment. Shortly after the ban, Sonnen stated he would have to find alternative methods to raise his testosterone or retire.
"If (the ban) retires guys, then it retires guys," Sonnen said on UFC Tonight. "Rules are rules and the rules need to be followed.
"I've had to stop testosterone with the hope we can find a new way to gain results of upping testosterone to a healthy level. If it doesn't work, I may have to stop the sport and it's as simple as that."
Sonnen was originally scheduled to fight Wanderlei Silva at UFC 175, which takes place at the MGM Grand Garden Arena in Las Vegas, but Silva was pulled from the card last month when he refused to submit to a random NSAC test.
Belfort (24-10) is facing a licensing issue in Nevada as well. The Brazilian had also been approved the use of TRT in his last three fights, but has since discontinued use. He is currently scheduled to appear at an NSAC licensing hearing on June 17.
This is the second time Sonnen has technically failed a drug test. In August 2010, he tested positive for an elevated testosterone-to-epitestosterone ratio prior to a UFC middleweight title fight against Anderson Silva in Oakland. The California State Athletic Commission suspended Sonnen for one year.