Last weekend, Anderson Silva defeated Nick Diaz by unanimous decision at UFC 183 in Las Vegas. Silva is a former middleweight champion making his first fight in over a year after an injury, and he was looking to begin his quest to get back to the top of the division.

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According to ESPN, Silva failed one of his pre-fight drug tests, testing positive for steroids. The test was administered on January 9, and Silva tested positive for two different steroids, drostanolone and androstane.

The results of the drug test were not available until Tuesday, which is why the fight was not canceled due to the positive test.

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Nick Diaz also failed a drug test that was administered after the fight, testing positive for marijuana metabolites. Exact results were not available, but Diaz was above the limit of 150 ng/mL.

"On Feb. 3, 2015, the UFC organization was notified by the NSAC that Anderson Silva tested positive for drostanolone metabolites on his Jan. 9 out of competition drug test," the UFC said in a statement. "UFC's understanding is that further testing will be conducted by the commission to confirm these preliminary results.

"Anderson Silva has been an amazing champion and a true ambassador of the sport of mixed martial arts and the UFC, in Brazil as well as around the world. UFC is disappointed to learn of these initial results."

Each fighter could face a fine and a suspension for their positive drug test. It is likely that each fighter will be temporarily suspended until they can have a disciplinary hearing.

This is the first positive test for any banned substance in Silva's career, but it is the third time Diaz has tested positive. All three of Diaz's violations were marijuana-related.