Former UFC lightweight and welterweight champ BJ Penn has been pulled from his scheduled UFC 199 bout with Cole Miller due to an apparent violation of the UFC’s Anti-Doping Policy.

The UFC said in an official statement: “The UFC organization was notified today that the U.S. Anti-Doping Agency (USADA) informed BJ Penn of a potential Anti-Doping Policy violation. Penn disclosed the usage of a prohibited method – the use of an IV in excess of 50 ML in a six-hour period – during a March 25, 2016, out-of-competition sample collection. In accordance with the UFC Anti-Doping Policy, Penn has received a provisional suspension, and has been removed from his scheduled bout against Cole Miller on June 4 in Los Angeles.

“UFC will announce a replacement opponent for Miller shortly, and additional information will be provided by USADA and UFC at the appropriate time as the process involving Penn moves forward.”

Penn has since released the following statement via “I voluntarily disclosed to USADA that during a non-fight period that I had an IV administered under the care of a doctor. The rule for IV usage had changed since my last fight in the UFC and was unaware of the change and voluntarily disclosed the information to USADA. I had no idea that IV use was banned 365 days a year.

“At no time in my career in martial arts have I ever doped and anticipate all test results from USADA will come back clean and will be working with the UFC to get the matter cleared up and return to fight as soon as possible.”

Penn has not competed in MMA since his TKO loss to Frankie Edgar at the TUF 19 Finale in July 2014. Penn announced his retirement after the loss. His comeback was confirmed earlier this year, but his future in the sport now looks uncertain as the veteran fighter could receive a fine and suspension as punishment for this violation.