Florida Agriculture Commissioner Charles Bronson says "very preliminary results" received this afternoon of necropsies done on the horses have not identified a cause.
"The necropsies found no remarkable signs that could indicate a specific cause of death," Bronson said.
He said state officials will continue their investigation and will be doing additional testing of tissue samples to determine if they contain any toxins. They will also be conducting laboratory tests on blood samples.
"The initial review of the horse carcasses did not show any visible signs of trauma or disease that would indicate an obvious cause of death," Bronson said.
"Our specialists will continue conducting more detailed testing until we get to the bottom of this tragedy."
State veterinary officials say the "gross necropsies", which involve a visual inspection of the organs, only showed damage that was consistent with the clinical signs the horses were exhibiting before death. This included some lesions in the trachea and larynx which can be explained by the respiratory problems the horses were having before death.
State officials say all the evidence they have indicates this is not a contagious disease. They have returned to the stables in Wellington that housed the animals and the polo facilities and say there are no additional cases of illness or deaths.
Bronson's Office of Agricultural Law Enforcement is working with Palm Beach County law enforcement to gather facts about the incident to determine the direction of the investigation.