Arms Runner became the 23rd horse to die at Santa Anita since the start of racing season on Dec. 26 after falling on the dirt crossover portion of the track Sunday.
Arms Runner was competing in the $100,000 San Simeon Stakes, the feature race of the day, when he appeared to injure his right front leg.
Santa Anita had just reopened Friday for the first time since March 3, as officials had tried to determine the reason for the numerous deaths.
Princess Lili B was the 22d fatality, on March 14, when she broke her front legs during a training run.
This article was originally published by Espn.com. Read the original article here.