Cycling. Baseball. Track. Horse racing. Now dogsledding has become the latest professional sport to be engulfed in a doping scandal, this one involving the huskies that dash across the frozen landscape in Alaska’s grueling, 1,000-mile Iditarod.

The governing board of the world’s most famous sled dog race disclosed on Monday that four dogs belonging to Dallas Seavey had tested positive for a banned substance, the opioid painkiller Tramadol, after his second-place finish last March.

It was the first time since the race instituted drug testing in 1994 that a test came back positive.

Seavey strongly denied giving any banned substances to his dogs, suggesting instead that someone may have sabotaged their food, and race officials said he would not be punished because they were unable to prove he acted intentionally. That means he will keep his titles and his $59,000 in winnings this year.

But the finding was another blow to the Iditarod, which has seen the loss of major sponsors, numerous dog deaths, attacks on competitors and pressure from animal rights activists, who say huskies are run to death or left with severe infections and bloody paws.

People for the Ethical Treatment of Animals (Peta) seized on the scandal on Tuesday.

“If a member of the Iditarod’s ‘royalty’ dopes dogs, how many other mushers are turning to opioids in order to force dogs to push through the pain?” Peta said in a statement. It added: “This doping scandal is further proof that this race needs to end.”

Fern Levitt, director of the documentary Sled Dogs, an exposé on the treatment of the huskies, said: “The race is all about winning and getting to the finish line despite the inhumane treatment towards the dogs.”

Earlier this year, the annual Anchorage-to-Nome trek lost a major corporate backer, Wells Fargo, and race officials accused animal rights organizations of pressuring the bank and other sponsors with “manipulative information” about the treatment of the dogs.

Five dogs connected to this year’s race died, bringing total deaths to more than 150 in the Iditarod’s 44-year history, according to Peta’s count. And last year, two mushers were attacked by a drunken man on a snowmobile in separate assaults near a remote village. One dog was killed and others were injured. The attacker was given a six-month sentence.

Seavey won the Iditarod in 2012, 2014, 2015 and 2016 and has had nine straight top-10 finishes. He finished second this year to his father, Mitch, who collected a first-place prize of $71,250.

Dogs are subject to random testing before and during the race, and the first 20 teams to cross the finish line are all automatically tested.

“I’m probably the only person in the world that knows definitively I did not give a drug to my dog. I’ve never used a banned substance in the race,” the 30-year-old Seavey said in an interview.

In a video posted on his Facebook page, he said that security was lax along the route and that someone might have tampered with his dogs’ food. He added that he wouldn’t be “thrown under the bus” by the race’s governing board and that he had withdrawn from the 2018 race in protest.

Seavey said he expected the Iditarod Trail Committee to ban him from the race for speaking out. Mushers are prohibited from criticizing the race or sponsors. An Iditarod spokesman, Chas St George, said that decision would be up to the committee’s board of directors.

The committee decided to release the name of the offending musher on Monday after scores of competitors demanded it do so. Race officials initially refused to release the name because, they said, it was unlikely they could prove the competitor acted intentionally and because a lawyer advised them not to make the name public.

At the time of this year’s race, the rules essentially said that to punish a musher, race officials had to provide proof of intent. The rules have since been changed to hold mushers liable for any positive drug test unless they can show something beyond their control happened.

Wade Marrs, president of the Iditarod Official Finishers Club, said he did not believe Seavey intentionally administered the drugs to his animals. Marrs said he believed the musher had too much integrity and brains to do such a thing.

“I don’t really know what to think at the moment,” Marrs said. “It’s a very touchy situation.”