Santa Anita officials confirmed that a horse, which had been training at the park Sunday morning, died but did not immediately provide details.
A horse named Tikkun Olam suffered catastrophic injuries, but the riders and other horses were not injured, an official told Eyewitness News.
News of the death came as protesters returned to the park to once again call for a ban to the sport of horse racing.
The sport, they said, too often results in injuries, and euthanization, to the horses.
"They call these horses equine athletes," said protester Andrew Lesser. "They're nothing more than equine gladiators."
That follows the deaths of two horses in the previous two days at the park, which has faced increased scrutiny since a string of publicized horse deaths dating back to 2018.
There have now been 42 horse deaths at the park since December 2018.
The 4-year-old gelding, Uncontainable, was "humanely euthanized" after suffering a fractured right front ankle, according to an incident alert on the race track's website.
Another horse, a 6-year-old gelding named Harliss, was also euthanized Friday after fracturing his right front ankle during a race, bringing the total number of horse deaths to 41 since December 2018.
The season opened late last month with the news of the death of 3-year-old gelding named Truest Reward after sustaining an injury while training.
As new season opens, another horse dies at Santa Anita - 38th death in the past year
Park officials have said they have made safety improvements at the track in the past year, including a new PET Scan machine. The device provides imaging of the fetlock or ankle joint - the most common area for injuries to occur in Thoroughbreds -- without horses having to undergo anesthesia, and said it will help to diagnose pre-existing conditions in Thoroughbred racehorses.
RELATED: Santa Anita Park unveils standing PET scan machine for horses
On Saturday, after the second horse death was announced, the racetrack issued a statement reaffirming its commitment to safety.
"Santa Anita remains committed to transparency,'' the statement said. "Our safety statistics and incident reports are publicly available on our website at SantaAnita.com/safety. Home to 2,000 horses, Santa Anita Park is one of the largest equine training facilities in the United States. Horses raced or trained at Santa Anita Park more than 420,000 times over the last year with a 99.991% safety rate.''
City News Service contributed to this report.