The return of MMA legend B.J. Penn will have to wait. The UFC announced Monday that Penn has been pulled from his UFC 199 bout against Cole Miller and provisionally suspended for a "potential Anti-Doping Policy violation" with the U.S. Anti-Doping Agency (USADA).

According to a UFC statement, Penn disclosed the use of an IV "in excess of 50 mL in a six-hour period" during a USADA out-of-competition drug test taken on March 25.

The use of IVs over 50 mL per six-hour period are prohibited both in-competition and out-of-competition by World Anti-Doping Agency guidelines, "except for those legitimately received during a hospital admission, surgical procedure, or as part of a diagnostic clinical investigation."

The UFC are currently searching for a replacement opponent to fight Miller.

In a statement released on Penn's website, Penn indicated that he was unaware of the ban on IV use -- a ban which was not in effect at the time of his last fight in 2014.

"I voluntarily disclosed to USADA that during a non-fight period that I had an IV administered under the care of a doctor," Penn said.

"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."

The UFC's statement can be read below.

"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 (16-10-2) is a 37-year-old former UFC lightweight and welterweight champion who last competed in July 2014, when he lost via third-round TKO to Frankie Edgar. A UFC Hall of Famer, Penn retired after the Edgar fight, but announced intentions to return to the sport this past February under the guidance of Team Jackson-Winkeljohn in Albuquerque, N.M.

UFC 199 takes place June 4 at The Forum in Inglewood, California. The event is headlined by two title fights, as Luke Rockhold looks to defend his middleweight championship against Michael Bisping, and bantamweight king Dominick Cruz takes on rival Urijah Faber.