The Stronach Group is the owner of Santa Anita Park, the of 24 horse deaths over a span of five months. (Amanda Lee Myers/AP, File)

As horse racing reels from the shocking death of a horse on Friday at Baltimore’s Pimlico Race Course that marred the weekend of the Preakness Stakes, another horse was killed training across the country at historic Santa Anita Park, thrusting the sport further into controversy during its most important period of the season.

Commander Coil, an unraced 3-year-old gelding, broke down of a shoulder injury during a routine gallop in training hours at the California racetrack. He is the 24th horse to die there since Dec. 26, and track executives still have yet to identify the underlying cause of the fatalities. One executive called the issues “multi-factorial,” but soil experts have not discovered anything unusual at the 84 year-old facility.

California Sen. Dianne Feinstein (D) has called for the state’s horse racing commission to halt racing until four full-time investigators conclude their work studying the horses’ deaths, and state legislators have pledged to hold hearings on the state of the track.

Officials halted racing there in March after 21 equine deaths in a three-month span, but another horse, 3-year-old filly Princess Lili B, was killed after breaking both legs at the conclusion of a timed workout the day after the track reopened. Two weeks later, 5-year-old gelding Arms Runner, broke down during a fall on the turf course.

Before Commander Coil’s death, Santa Anita had gone six weeks without a horse fatality.

“Equine shoulder injuries are rare, especially for a horse that is galloping as opposed to breezing or racing. A comprehensive evaluation will be completed to understand what might have caused this uncommon injury,” Santa Anita owner The Stronach Group said in a statement. The company also owns Pimlico Race Course.

“The Stronach Group remains committed to operating Santa Anita Park with stringent protocols that prioritize the health and safety of horses and riders first and foremost.”

The same day, Congrats Gal, a 3-year-old filly, collapsed of what veterinarians suspect to be a heart attack after the Miss Preakness Stakes at Pimlico.

“The sickening collapse and sudden death of Congrats Gal at Pimlico are proof that the Maryland racing industry has not done enough to protect horses,” Kathy Guillermo, senior vice president of People for the Ethical Treatment of Animals, said in a statement. “ . . . We will be contacting the district attorney’s office, as we did in California, where the D.A. has appointed a task force to investigate training and veterinary practices.”

Congrats Gal’s death casts an even darker shadow over Saturday’s $1.5 million Preakness, the middle jewel of horse racing’s Triple Crown. The race is already without Kentucky Derby winner Country House, the first Derby champion in 23 years to skip the Preakness, as well as Maximum Security, the horse that crossed the finish line first at Churchill Downs — only to be disqualified for veering across multiple lanes of traffic. Country House was declared the winner after a 22-minute review.

In the aftermath of the controversial finish, owners, trainers and jockeys traded barbs over the stewards’ decision, and Maximum Security’s owner, Gary West, sued the Kentucky Horse Racing Commission to reverse the race’s official result. Jockey Luis Saez, who rode Maximum Security in the Derby, was suspended 15 racing days for failure to “control and guide his mount.”

Dave Sheinin in Baltimore contributed to this report.

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