IBF, IBO, WBA, WBC middleweight champion Gennady Golovkin (37-0-1, 33 KOs) has decided to double-down on his accusations that upcoming opponent Saul "Canelo" Alvarez (49-1-2, 34 KOs) is a longtime user of performance enhancing drugs.

Canelo tested positive for banned drug clenbuterol in drug tests conducted by the Voluntary Anti-Doping Association (VADA) on February 17 and February 20. He has since tested negative in three tests conducted in March.

Golovkin has been calm since the information of the positive tests came out, but on Tuesday the boxer erupted during a group interview with reporters at his training camp in Big Bear Lake, California.

Golovkin rejected Canelo's claim that his positive tests were a direct result of digesting contaminated meat - which is ongoing problem for athletes from Mexico, because farmers use the banned drug on cattle to increase lean muscle mass.

"Again with Mexican meat? Come on," Golovkin said. "I told you, it's not Mexican meat. This is Canelo. This is his team. This is his promotion. Canelo is cheating. They're using these drugs, and everybody is just trying to pretend it's not happening.

"This guy, he knows. This is not his first day in boxing. He proves he gets benefits from everyone and he can get away with it. Check him on a lie detector and then we can find out everything."

Of course Golovkin also stated that he knew Canelo was "not a clean fighter" before their first encounter last September.

Golovkin obtained photographs and videos, which the boxer claims reveal traces of "injections" on Canelo's body and also show him taking an unknown pill.

"It was pretty obvious when [Canelo's] muscles were all [enlarged] ... and with the traces of injections, which were visible," Golovkin said. "Before the first fight, I knew he was not clean. I can talk about Oscar De La Hoya too. He is also not clean. He's dirty."

When speaking later to ESPN, Golovkin once again stamped down his accusations.

"I think it is silly to blame the meat because an athlete at this level should not be caught on the meat. I eat Mexican food all the time and I've never had that problem," Golovkin said.

"If nobody from the commission will cancel it, I will do my job. But this is a very hot topic about doping. What did he inject in his belly? What are the marks on his belly? Look at the photos. These questions should be asked of the commission."

Golovkin's promoter, Tom Loeffler, also gave his take on the matter to ESPN.

"People were sending him videos and photos, and they said he should ask the commission what these photos and videos are," Loeffler said.  "People were telling him to get the commission to clarify what it was. But he doesn't think Canelo was smart."

The two athletes are scheduled to collide for a second time on May 5th at the T-Mobile Arena in Las Vegas.