Florida ? Organ by organ, veterinarians are taking apart 21 prized polo horses to uncover what killed them mysteriously over the weekend during preparations for a match in one of the sport’s top championships. Simultaneously, state authorities have opened a criminal probe to determine whether the deaths were intentional, a result of negligence or simply a terrible accident.

With careful cuts to their muscular bodies, the investigators look for lesions, fluids, bruises and hemorrhages, any obvious signs of sickness. They’re removing the hearts, lungs, livers, kidneys and spleens, and cutting small samples to be tested for toxins. The process unfolds much as it would for a dead person.

State officials believe the horses died from an adverse drug reaction, toxins in their food or supplements, or a combination of the two. Two days after the horses’ deaths, authorities say they have not uncovered any crime but continue to investigate.