UFC 219 fighter Michal Oleksiejczuk failed a U.S. Anti-Doping Agency (USADA) drug test and has been notified of a potential UFC anti-doping policy violation.

Officials today announced the news, via UFC.com.

Oleksiejczuk (13-2 MMA, 1-0 UFC)’s failed test was the result of an in-competition sample collected in conjunction with UFC 219. At the Dec. 30 event, he upset heavy favorite and fellow light heavyweight Khalil Rountree (6-3 MMA, 2-3 UFC).

From USADA:

“The UFC organization was notified today that the U.S. Anti-Doping Agency (USADA) informed Michal Oleksiejczuk of a potential Anti-Doping Policy violation stemming from an in-competition sample collected in conjunction with his recent bout against Khalil Roundtree at UFC 219 in Las Vegas, Nevada on December 30, 2017.

“USADA, the independent administrator of the UFC Anti-Doping Policy, will handle the results management and appropriate adjudication of this case involving Oleksiejczuk, as it relates to the UFC Anti-Doping Policy and future UFC participation. Because the Nevada Athletic Commission was the regulatory body overseeing the fight in Las Vegas and has licensing jurisdiction over Oleksiejczuk, USADA will work to ensure that the Nevada Athletic Commission has the necessary information to determine its proper judgment of Oleksiejczuk’s potential anti-doping violation. Additional information will be provided at the appropriate time as the process moves forward.”

Oleksiejczuk, a 22-year-old Polish fighter, moved his current winning streak to 10 fights with the UFC-debut win, though the result could be overturned.

For complete coverage of UFC 219, check out the UFC Events section of the site.