(CNN) -- A horse at Santa Anita Park in California sustained a fatal injury Thursday following a half-mile workout, park spokesman Mike Willman said.
It's the 22nd horse death since December 26. Last year, 10 horses died at Santa Anita over the same period.
The 3-year-old filly, Princess Lili B, "must have taken a funny step," causing her to break two ankles, trainer and owner David Bernstein told CNN affiliate KTLA. She had to be euthanized, he told the station.
She was "was doing extremely well," and her rider noticed nothing odd about her performance, said Bernstein, who had raised the horse since she was born.
The 1-mile main track reopened Monday and remains open for limited training.
It closed March 5 for evaluation, and officials indefinitely suspended racing after Debbie McAnally's horse became the 21st to die this season at Santa Anita. The 4-year-old filly was euthanized after shattering her front leg on a training run.
After reopening this week, the park said training at the Arcadia, California, track was "restricted to joggers and gallopers," referring to gaits for horses.
"Over the past four days, we've been able to do a great deal in terms of amending the soil and inspecting it," Dennis Moore said in a statement. Moore has been retained as a consultant to inspect the track's condition.
The deaths have spurred numerous questions. Were drugs administered to the horses to blame? Were the horses running too hard?
Many people connected with Santa Anita Park, however, said they believe rain is a factor. Southern California has been having its wettest winter in almost a decade.
"The ground gets too soft," said Jim Cassidy, president of the Thoroughbred Trainers Association.
He said the track was to blame for a catastrophic injury that led a horse he trained to be put down.
In preparation for storms, a sealant is used keep the surface from washing away, but Cassidy claims that once the rain is over, the track "is too hard."
Moore has been reviewing soil samples and test data from Mick Peterson, a third-party consultant and director of the University of Kentucky's Agricultural Equine Programs, the park said.
Peterson is as perplexed as everyone, but, like Southern California drivers unaccustomed to driving in wet conditions, he suggests the trainers and track officials may be unaccustomed to dealing with so much inclement weather.
The park dates back to 1907 and was a filming location for the movie "Seabiscuit."
Additional testing with a veteran track expert will use a machine Peterson invented that mimics the response of the front leg of a racehorse at a full gallop. Peterson's findings are now a part of a larger review underway.
"It's like the National Transportation Safety Board coming in after a plane crash and piecing everything together," he said. And like the NTSB review, it could take months.
Bernstein told KTLA he had no idea what could be causing the fatal injuries. The track is in "marvelous condition," he said.
"I know they've done the best job they can do. They've hired a number of great experts," he said. "I wouldn't hesitate to go out tomorrow."
The racetrack dates back to 1907 and has been a prominent location in the racing community. In 1940, Seabiscuit won the Santa Anita Handicap, and in 2002 the park was a filming location for the movie named after him.
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