A 27th horse has been euthanized after it was injured at Southern Californias Santa Anita racetrack, the latest in a string of mysterious fatal injuries since late December.

The 2-year-old unraced colt named River Derby suffered a fractured shoulder while galloping during training Wednesday morning, the Los Angeles Times reported.

The horse was taken to an equine hospital in Chino for possible surgery, but upon his arrival it was determined that surgery was not an option. He was euthanized and a necropsy will be performed, Mike Marten, spokesman for the California Horse Racing Board, told HuffPost in an email.