Horse racing legend Bob Baffert came under scrutiny on Sunday after it was revealed his record-breaking Kentucky Derby-winning colt Medina Spirit failed a post-race drug test.

It is the fifth time a horse trained by him fails a drug test.

In 2018, Justify captured the Triple Crown, winning the Derby, Preakness Stakes and Belmont Stakes. It was the second horse to win the Triple Crown with an undefeated record. However, The New York Times reported in 2019 that Justify tested positive for the banned substance scopolamine before the Santa Anita Derby – a precursor race to the Derby where he needed to win or show in order to race at Churchill Downs.

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According to the Times at the time, California regulators waited almost a month to tell Baffert his horse had failed a performance-enhancing drug test. Later, officials would reportedly determine the positive test could have come from "eating contaminated food" and dismissed the case.

In July 2020, the Arkansas Racing Commission suspended Baffert for 15 days after two of his horses tested positive for a banned substance. Both horses tested positive for lidocaine, The New York Times reported. Baffert said at the time his horses were inadvertently exposed to the substance.

One of the horses in the July controversy, Gamine, also tested positive for increased levels of betamethasone in post-race testing last October. The Kentucky Public Protection Cabinet, which regulates horse racing, said at the time the sample of an unidentified horse indicated a Class C medication violation. Baffert’s attorney later identified the horse as Gamine.

Baffert’s attorney said at the time the drug was administered 18 days before the Kentucky Oaks. State rules require at least a 14-day withdrawal time and any level of detection on race day is a violation.

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Medina Spirit also tested positive for betamethasone. Baffert said his barn was told Medina Spirit had 21 picograms of betamethasone in a post-race sample – more than double what the trainer said was the allowable amount.

Animal Wellness Action executive director Marty Irby released a statement on the horse-racing controversy.

"The latest doping scandal in U.S. horse racing underscores the need for swift implementation of the Horseracing Integrity and Safety Act that will address inconsistencies in drug testing and create a uniform national standard of rules and regulations in the sport," Irby said.

"If further investigation finds Medina Spirit legitimately tested positive for illegal drugs at the Kentucky Derby, then racing authorities should throw the book at those found guilty of violating the rules and punish them to the fullest extent of the law. American horse racing will be held to a higher standard – there’s no excuse for rigging the ‘fastest two minutes in sports,’ especially at the expense of the horse’s well-being."

Baffert denied any wrongdoing and promised to be transparent with the Kentucky Horse Racing Commission during its investigation.

"I got the biggest gut-punch in racing for something that I didn’t do," Baffert said of the result. "And it’s disturbing. It’s an injustice to the horse. ... I don’t know what’s going on in racing right now, but there’s something not right. I don’t feel embarrassed. I feel like I was wronged. We’re going to do our own investigation. We’re going to be transparent with the racing commission, like we’ve always been.

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"He’s a great horse. He doesn’t deserve this. He ran a gallant race."

Medina Spirit is still expected to race in Saturday’s Preakness Stakes.

The Associated Press contributed to this report.