Santa Anita Park has closed at least through the weekend because of a high number of horse deaths.
CNN  — 

Santa Anita Park in Arcadia, California, will reopen for “limited training” Monday morning, after racing was suspended last week in response to the deaths of 21 racehorses since December 26.

The track, which has been closed since Tuesday, will be “restricted to joggers and gallopers,” a statement from the park said, 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, who was retained as a consultant to inspect the condition of the one-mile track, said in the park’s statement.

Nobody knows why 21 horses died while racing or training at the track in 10 weeks. Only 10 horse deaths occurred during the same period last season.

The company that runs Santa Anita Park announced new safety measures Friday in response to the deaths.

“We need to work together and continue to create not only our own internal audits, but an open and honest dialogue with all of the stakeholders and evaluate best practices at other racetracks around the world,” Tim Ritvo, chief operating officer for The Stronach Group (TSG), said in a statement.

TSG said changes for the track include:

• Trainers must seek permission 24 hours in advance to “work” a horse – a timed high-speed training exercise.

• More track veterinarians have been hired to identify at-risk horses by evaluating past performances, workout data and physical inspection.

• A new position, director of equine welfare, was created to oversee the well-being of horses and lead a new rapid response team to investigate horse injuries.

• The track will require that veterinary records follow a horse through any trainer or ownership change.

• The first 15 minutes of training after the main track opens are reserved for horses working for an officially clocked time. This should allow faster horses going at a faster pace to encounter less traffic.

Trainers, owners and track officials are baffled by the high number of deaths. Some people think an unusually rainy period may have made affected the running surface.

It's unclear when Santa Anita Park will reopen, as an investigation into the deaths is underway.

As part of his investigation, 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 Program, the park said.

Moore said it is “very helpful” that the track has not received significant rain since Wednesday.

“We’ve reviewed Mick’s research and it clearly indicates our cushion is right where it needs to be,” Moore said in the statement. “We also acknowledge that things can happen even under perfect circumstances, but from everything we’ve been able to learn, this track is in outstanding condition and it’s ready for training.

PETA has called for the track to close. “The only responsible action is for the track to close right away and stop this spiral of deaths,” the group said in a statement.

Santa Anita Park was scheduled this weekend to host the Santa Anita Handicap, a race for older horses, as well as the San Felipe Handicap, an important preparatory race to qualify for the Kentucky Derby.

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.

CNN’s Stephanie Becker and Madeline Holcombe contributed to this report.