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LOUISVILLE, Ky. (AP) — There’s growing concern over the safety of horses running in Saturday’s Kentucky Derby, considering four horses died after training in just the last week at Churchill Downs.

The recent deaths of the race horses at the iconic track raises questions about safety of the sport ahead of the 149th run for the roses.

On Thursday, Churchill Downs suspended Saffie Joseph Jr, who trained two of the horses that collapsed on the track and died after races earlier this week.

Despite the horse deaths, Joseph was still planning to put one of his other horses named Lord Miles in the race. Because Joseph is suspended, racing officials banned Lord Miles from being in the race.

“It shatters you,” Joseph said, his voice breaking. “Anyone around me knows how much I care about my horses. Whether it just be a small issue, I care. When you care, it hurts.”

No cause of death of Joseph’s horses has been determined. Race horses, which can weigh 1,200 pounds and run 45 MPH, can and have suffered sudden death for health reasons after races, and workouts.

Two other Derby longshots belonging to other trainers, suffered injuries after races earlier this week, and were euthanized.

Part of the Horseracing Integrity and Safety Act (HISA) took effect last summer, but new antidoping rules have been delayed by court challenges.

Those regulations won’t be implemented until after this year’s Kentucky Derby.

“We should have had federal authority in place by now for testing horses and making sure the race day anti-doping provisions and other provisions of the law were being enforced,” said Wayne Pacelle, president of Animal Wellness Action. “It’s like the Miami Dolphins having different rules in Florida for football compared to the Detroit Lions. It doesn’t make sense.”

Some horse racing officials have been concerned breeding practices that produce faster horses increase the risk of other health problems.

150,000 people are expected to be at Churchill Downs to watch 19 horses race in the 149th Kentucky Derby Saturday evening.