DAYTON, Ohio (WDTN) — Churchill Downs is speaking out after four horses were reported dead, just days before the Kentucky Derby.

On Wednesday, May 3, the horse racetrack released information about the horses who suffered injuries. Wild On Ice was training on the dirt Thursday, while Take Charge Briana was participating in the turf race on Tuesday. Both horses sustained musculoskeletal injuries. The two horses were euthanized “for humane reasons,” Churchill Downs said in the statement.

Two more horses, Parents Pride died suddenly on Saturday and Chasing Artie died on Tuesday, both from unknown causes. Parents Pride and Chasing Artie were both trained by Saffie Joseph Jr.

“While a series of events like this is highly unusual, it is completely unacceptable. We take this very seriously and acknowledge that these troubling incidents are alarming and must be addressed.”

All four horses were reportedly taken to the University of Kentucky’s Veterinary Diagnostics Lab to have “complete necropsies” conducted.

Churchill Downs says they are conducting a thorough investigation into why the horses were injured.