The reigning Horse of the Year, Curlin, was treated with anabolic steroids last year but was taken off the drugs in January, the New York Times reported on Thursday, citing comments made by Jess Jackson, the majority owner of the colt.

Jackson also told the Times that he would pay for independent testing of his horses, beyond that already done by racing commissions, which typically test the first three finishers in a race. Jackson said he warned the trainers of his more than 60 horses, including Steve Asmussen, Curlin's trainer, that they would be fired if a horse tests positive for a performance-enhancing drug.

"I'm against all performance-enhancing drugs, or anything that masks or conceals designer drugs," Jackson was quoted as saying in the Times. "I have been for zero tolerance since the 1950s. We have to start bringing our horses down from all these chemicals."

Jackson recently appeared before a federal congressional subcommittee and testified that he believed the U.S. should have "zero-tolerance" rules on medication.

According to Jackson's publicist, Caroline Shaw, Jackson was flying from Hawaii to Kentucky on Thursday and was unavailable for comment.

Asmussen was recently notified that one of his horses tested positive in Texas for lidocaine, an anesthetic. But Jackson told the Times that he believed Asmussen and his attorney when they said that the positive was a mistake or the result of a faulty test. A stewards' hearing on the case has been set for Sept. 9 at Lone Star Park.

According to the Times, Jackson said that Curlin has not received steroids since January, when the horse would have had to withdraw from the drugs in order to test clean for two races in Dubai, where anabolic steroids are illegal. In Dubai, Curlin won the Feb. 28 Jaguar Trophy Handicap and the March 29 Dubai World Cup, both at Nad Al Sheba racecourse. Curlin has made one start in the United States since returning from Dubai, winning the June 14 Stephen Foster Handicap at Churchill Downs in Kentucky.

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Steroids were legal to administer last year in nearly every major racing jurisdiction in the United States, and are still legal in a number of states. Many states are in the process of adopting rules that will allow for the use of four anabolic steroids as long as they are administered 30 days outside of a race. All other anabolic steroids will be prohibited under the rule.

Curlin is entered in the Man o' War on Saturday at Belmont, his turf debut. If he runs well, he will be shipped to France for possible starts in the Sept. 14 Prix Foy and the Oct. 5 Prix de l'Arc de Triomphe. Steroids are illegal in France and all other European countries. As in Dubai, veterinarians recommend that horses not be administered anabolic steroids within 45 days of racing in Europe.

The issue of drugs in racing, and particularly anabolic steroids, has been a focus of the general public this year. It has led some owners to make public pronouncements of their commitment to abide by racing's medication rules, including IEAH Stables, the majority owner of Kentucky Derby and Preakness Stakes winner Big Brown. IEAH said last month that as of Oct. 1, horses owned by the group would not be administered any anabolic steroids.