The deaths of four horses have raised alarms at Churchill Downs Racetrack, the site of this week's Kentucky Derby.
Two of the horses died suddenly within the last week, racetrack officials stated.
The two other horses were injured while training and were euthanized for humane reasons, officials said.
According to Churchill Downs, Wild on Ice died on Aug. 27 after training on the dirt track, and Take Charge Briana died after training on the turf track.
None of the horses that died were due to race in the Kentucky Derby.
"While a series of events like this is highly unusual, it is completely unacceptable," Churchill Downs said in a statement. "We take this very seriously and acknowledge that these troubling incidents are alarming and must be addressed."
Officials said the bodies of all four of the horses were taken to the University of Kentucky Veterinary Diagnostics Lab to determine their exact cause of death.
Twenty horses will compete in Saturday's Kentucky Derby.
Forte is the favorite to win with 3-1 odds. In seven races, he's placed first six times.
Post time for what's described as "the most exciting two minutes in sports" is set for Saturday at 6:57 p.m. ET.
Churchill Downs said it's been assured the track is safe for the big race and others preceding it.
"We have full confidence in our racing surfaces and have been assured by our riders and horsemen that they do as well," Churchill Downs said.
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