Originally Published: 03 MAY 23 17:12 ET

By David Close, CNN

(CNN) -- Officials from the Churchill Downs racetrack, the home of the famed Kentucky Derby, have described the recent deaths of four horses as "unacceptable" and "troubling."

The four race horses have died in separate incidents within a five-day stretch.

Since the start of Kentucky Derby week -- on April 29 -- two horses died suddenly from unknown causes at the track according to officials.

Parents Pride passed on Saturday and Chasing Artie on Tuesday. Both equines were trained by Saffie Joseph Jr.

"I'm shattered, basically, because I know it can't happen," Joseph told CNN affiliate WDRB on Wednesday.

"The odds of it happening twice is in the trillions. I run almost 4,000 horses and it's never happened. It doesn't make sense."

Joseph also trains the colt Lord Miles who is entered in the Kentucky Derby.

The 149th Derby, the first horse race in the coveted Triple Crown, is set to run Saturday in Louisville, Kentucky.

CNN has reached out to Joseph for comment.

According to Churchill Downs, two other horses died after suffering musculoskeletal injuries. Wild on Ice, a Derby contender, was hurt while training last Thursday and Take Charge Briana was injured during a race on Tuesday. Both were "euthanized for humane reasons."

In a Wednesday statement, officials said: "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."

Churchill Downs said it was "working with regulators to conduct swift and thorough investigations."

"The safety and well-being of horses is a critical issue for which everyone in the industry shares responsibility; however, we will continue to take every measure to ensure that we are providing the safest possible environment for horses on our property," added the Churchill Downs statement.