Four horses have died after running at Churchill Downs in the days leading up to the 149th Kentucky Derby on Saturday.

Two of the four horses, Chasing Artie and Parents Pride, were owned by Ken Ramsey, trained by Saffie Joseph Jr., and ridden by Luis Saez. Both of the horses died following turf races at Churchill Downs. Parents Pride collapsed and later died on Sunday, and Chasing Artie died on Tuesday.

The cause of the deaths is currently unknown and will not be known until necropsies are performed on each horse. Joseph said that something must be wrong and called for facts to be announced at the soonest possible moment.

“Something’s not right. These horses, it wasn’t because of injury. They left the gate and didn’t even try and then dropped down. Theories aren’t going to help. We need facts,” said Joseph, per the Courier Journal.

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Following the deaths of the two horses, Bill Mudd, the president and chief operating officer of Churchill Downs Inc., announced that Joseph would be suspended indefinitely.

“Given the unexplained, sudden deaths, we have reasonable concerns about the condition of his horses and decided to suspend him indefinitely until details are analyzed and understood,” said Mudd, per AP News. “The safety of our equine and human athletes and integrity of our sport is our highest priority. We feel these measures are our duty and responsibility.”

In addition to the horses owned by Ramsey, two other horses were euthanized due to leg injuries. Take Charge Brianna was euthanized after a “catastrophic injury suffered during R5 [race five] on turf,” tweeted Marty McGee, a correspondent for Daily Racing Form.

Wild on Ice was also euthanized due to a leg injury that was sustained during a morning training session on the dirt track at Churchill Downs. The horse was evaluated at the racetrack and then transferred to a facility in Lexington.

Frank Sumpter, Wild on Ice’s owner, released a statement confirming the death and expressing his condolences to the horse’s team.

“Wild On Ice gave us so many great moments,” said Sumpter, per the El Paso Times. “He’ll forever be remembered. It’s a sad situation. My heart goes out to the team, trainer Joel Marr and everyone who helped us get to this point. These horses give us so many great moments in life, and our team puts in so many hours taking care of the horses. He had a fracture in his hind leg, and it was determined he couldn’t be saved. Wild On Ice had so much heart.”

There are 1.25 deaths for every 1,000 starts in the last year, a decrease from the year prior, which saw 1.39 deaths for every 1,000 starts, per The New York Times. Tim Parkin, a professor of veterinary epidemiology at the University of Bristol in England, said there is confidence that injury and death risks will continue to decrease.

“We can say with confidence that the risk of fatal injury is heading in a sustained downward direction both overall and in many specific areas,” said Parkin, per The New York Times.