After six weeks of safe racing and training, Santa Anita has had its second horse death in four days.

A first starter pulled up in a race on Sunday was euthanised on Monday (Tuesday AEST) to bring up the 25th death at the track since December 26.

Spectacular Music was running in a maiden claiming race restricted to California-breds when jockey Jorge Velez pulled the horse up.

The gelding was found to have a pelvis injury an, after initial attempts to save him, the decision was made to put him down.

On Friday, Commander Coil was euthanised after suffering a shoulder-area injury during a routine training gallop.

The two injuries are similar only in that they are not the most common injuries. Most catastrophic injuries to horses occur in the fetlock or joint area of the leg, not the shoulder area or pelvis.

"You'll find that there are pre-existing conditions on most scapular (shoulder blade), pelvic, lumbar (spine), humerus and tibia (lower leg) injuries," Rick Arthur, chief equine veterinarian of the CHRB, said.

"But many are not clinically apparent. The problem is they are hard to discover because they are covered by muscle. Horses with these injuries don't show lameness. They are very hard to pick up."

Arthur did not know what prior treatment either of the two horses had received.

The track was coming off a period in which it recorded almost 7000 timed work-outs and race starts without serious incident. Santa Anita estimates that around 80,000 horses had galloped during that period.