UFC star Anderson Silva said he didn't knowingly use the two substances flagged by the U.S. Anti-Doping Agency during a drug test last October.
Silva told TMZ Sports his lawyers are evaluating the veracity of the positive test with USADA in the hope of invalidating the results. He added that "maybe the supplements I'm using are contaminated."
USADA administrators originally collected the sample during an out-of-competition test in October, with the results coming back in November.
Although Silva hasn't been formally suspended, the positive test forced UFC to drop him from his main event fight against Kelvin Gastelum at UFC Fight Night 122. Michael Bisping replaced him and lost to Gastelum via first-round knockout.
MMA Fighting's Marc Raimondi reported earlier this month Silva tested positive for methyltestosterone and an unknown diuretic. Methyltestosterone is listed as an anabolic agent in the 2018 guide of banned substances for the World Anti-Doping Agency.
The Nevada State Athletic Commission issued a one-year suspension to Silva in August 2015 after he failed multiple drug tests. Raimondi cited Brazilian media outlet Combate in reporting Silva's representatives are attempting to have USADA ignore his 2015 suspension before making a final decision.
According to Raimondi, Silva could potentially face a four-year ban if USADA's ruling factors in his previous infractions.