ARCADIA (CBSLA) — Animal rights activists are calling on California Gov. Gavin Newsom to get involved after a another racehorse died at Santa Anita Park, just days after the racetrack reopened from a nearly month-long hiatus following a spate of horse deaths.

Arms Runner, a 5-year-old horse who won his last race at the park on Jan. 27, was in the lead when he fell on a portion of track that goes downhill and transitions from grass to dirt during Sunday’s Grade 3 San Simeon Stakes. His fall caused another horse, La Sardane, which quickly regained her feet and went back to running.

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However, Arms Runner suffered a severe and ultimately fatal injury to his right front leg. He was euthanized, and his death is the 23rd at the racetrack since December.

“It’s gut wrenching,” said Tim Ritvo of the Stronach Group, which owns Santa Anita Park. “We’ll continue to review, look at all the medical records of the horse, and review all the data that we can and continue to investigate the causes of this.”

Everything from the condition of the main racing track to medication to the use of whips has been under scrutiny at the racetrack since horses started dying at Santa Anita Park in late December. Racing has been suspended twice, and the second hiatus just ended Friday after nearly a month.

There has been a variety of factors in each of the deadly falls, and track officials haven’t been able to pinpoint one specific problem.

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“There’s been six on the grass, there’s been seven on the dirt during racing and the rest of them were on the training, at all different areas, all different places, different legs, right, in front, so we can’t find any one common denominator,” Ritvo said.

The California Board of Horse Racing had also met just last week to consider new rules for the safety of the horses. One rule that went into immediate effect was a reduction in a medication called Lasix, a diuretic that helps prevent horses from hemorrhaging.

People For the Ethical Treatment of Animals issued a statement following the horse death:

“This sickening video of Arms Runner in the last minutes of his life shows exactly why PETA is calling on Gov. Gavin Newsom to form an independent panel to investigate training and veterinary practices in California. While the implementation of new rules at Santa Anita racetrack last week represented the first progress in racing reform in decades, it was nowhere near enough to save these horses’ lives. The California Horse Racing Board needs to pass emergency rules right now banning all drugs and banishing all trainers with medication violations from California tracks. Anything short of this is inadequate.”

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The next race at Santa Anita Park is scheduled for Thursday, and track officials say it will continue as planned.