According to the Daily Racing Form, a three-year-old filly collapsed and died of an apparent heart attack during a race Sunday.
Another horse had to be euthanized Saturday after suffering an injury during a race.
The California Horse Racing Board says Santa Anita management has refused its request to suspend racing at the track for the final week of the season.
The board does not have the authority to suspend racing without giving 10 days notice for a public meeting.
Animal-rights activists have been calling for an end to racing at the park.
"We keep coming back every week because of the carnage happening at this track," said Heather Wilson with the group Horseracing Wrongs. "They're trying to do safety measures - this is beyond reform. Horse racing just needs to end."
Some protesters are also suing the track, claiming security unnecessarily roughed them up during a demonstration in March. The Los Angeles County District Attorney's office looked into the incident, but declined to file charges.