Trainer Bob Baffert on Thursday denied doping last year’s Triple Crown winner Justify after it emerged that the horse failed a drug test before last year’s Kentucky Derby.

US racing was rocked on Wednesday after the New York Times found that Justify had tested positive for the banned substance scopolamine weeks before winning the first leg of the Triple Crown.

In a statement, Baffert said that the scopolamine entered Justify’s system through contaminated feed, adding that the banned substance is found in a weed that grows throughout California.

“I unequivocally reject any implication that scopolamine was ever intentionally administered to Justify or any of my horses,” Baffert said. “Test results indicating trace amounts of the drug were undoubtedly the result of environmental contamination caused by the presence of jimson weed in feed, a naturally growing substance in areas where hay and straw are produced in California.”

Former California Horse Racing Board (CHRB) chairman Chuck Winner in a statement backed Baffert’s claim, saying that Justify was among multiple horses cared for by different trainers at Santa Anita that tested positive at the same time, an indication that contaminated feed was involved.

How the case was handled by the CHRB has come under scrutiny after the Times reported that the governing body took more than three weeks to notify Baffert that the horse had failed a test, advising him only nine days before the Kentucky Derby.

It was more than a month before the CHRB confirmed the test result, the newspaper said, and it was four months later — after Justify became the 13th Triple Crown winner — that the board voted at a closed-door session to dismiss the case.

The Times reported that the decision to dismiss rested on the determination that the positive test could have been the result of contaminated food, citing the presence of jimson weed in California.

“It would have been a complete miscarriage of justice for the CHRB to have taken action against Justify or Baffert, knowing full well that the horse was poisoned by an environmental contaminate and not injected with a substance,” Winner said.

CHRB executive director Rick Baedeker told the Times that Justify was allowed to run because the CHRB would have been unable to produce a definitive investigative report prior to the Kentucky Derby.