The 33rd horse to die at the Santa Anita Park in Southern California since December suffered a suspected heart attack, the horse's trainer told reporters.
Ky. Colonel, a 5-year-old gelding, went into cardiac arrest after going for a jog on the training track, trainer Richard Mandella told reporters, according to ABC Los Angeles station KABC.
Ky. Colonel last raced at Golden Gate Fields in Northern California and had five wins in 20 career starts, KABC reported. A spokesman for Santa Anita declined to comment on the cause of death until the necropsy is complete but confirmed that racing would resume on Sunday.
On Sept. 28, a 3-year-old colt became the 32nd horse to die at the track after sustaining a catastrophic injury on the second day of the fall meet, according to The Associated Press. Jockey Mario Gutierrez was tossed off but was not injured, AP reported.
Santa Anita Park has been under intense scrutiny since the number of horse deaths began piling up earlier this year.
In April, Los Angeles County District Attorney Jackie Lacey announced that a task force would investigate whether unlawful conduct or conditions affected the welfare and safety of the horses.
In June, when the death toll had climbed to 29, California Gov. Gavin Newsom called for the shutdown of the park after it did not heed the California Horse Racing Board's recommendation to suspend racing.
Santa Anita decided to continue racing because it believed that the reforms enacted earlier in the year were working, a spokesman for The Stronach Group, a company that owns the park, told ABC News in June.
The park announced a series of changes surrounding horse safety in March, including a "zero tolerance" policy for the use of almost all medication on racing day. Earlier this year, the California Horse Racing Board further voted to limit whips on racing day as well. There were no horse fatalities between April 1 and May 18.
Santa Anita Park will host the 2019 Breeders' Cup world championships on Nov. 1 and 2. The fall season will conclude on Nov. 3.