The dominoes continue to fall in the UFC's crusade for a cleaner sport.

The UFC announced Friday that two-time featherweight title contender Chad Mendes has been flagged for a "potential Anti-Doping Policy violation" stemming from an out-of-competition drug test collected by the United States Anti-Doping Agency (USADA). The UFC did not specify the nature of the banned substance found in Mendes' sample.

Mendes, 31, is currently the No. 4 ranked featherweight in the UFC's media-generated rankings. He has been out of action since Dec. 2015, when he suffered a first-round knockout loss at the hands of Frankie Edgar at The Ultimate Fighter 22 Finale.

The UFC's statement can be read below.

"The UFC organization was notified today that the U.S. Anti-Doping Agency (USADA) has informed Chad Mendes of a potential Anti-Doping Policy violation stemming from an out-of-competition sample collection. USADA, the independent administrator of the UFC Anti-Doping Policy, will handle the results management and appropriate adjudication of this case. It is important to note that, under the UFC Anti-Doping Policy, there is a full and fair review process that is afforded to all athletes before any sanctions are imposed. Additional information will be provided at the appropriate time as the process moves forward."

Mendes (17-4) has twice fought for the UFC featherweight title, losing to former longtime champion Jose Aldo via first-round knockout in 2012, then falling short via decision in a highly competitive rematch in 2014.

While Mendes holds a sterling 12-4 record in his time under the WEC/UFC banner, he has struggled of late, dropping three of his last four contests including a failed bid for the interim UFC featherweight title against Conor McGregor at UFC 189.

If the results of Mendes' flagged test prove to be accurate, it would mark the first drug testing failure of the Team Alpha Male product's career.