Upon arrival at the International Polo Club Palm Beach in Wellington on Sunday, two of the horses died while being unloaded from their trailers. "Others lasted about 45 minutes," according to Dr. Scott Swerdlin of the Palm Beach Equine Clinic, the South Florida Sun-Sentinel reported.
The horses were from the Lechuza Caracas Polo team. All of the horses, containers and bedding have been sent to laboratories for analyses.
It is still unclear what killed the horses but a necropsies and blood tests were being done, the Palm Beach Post reported.
Each team competing in the Open match brings between 40 and 60 horses and rotates them during the game so as not to tire them.
According to a polo club spokesman, Tim O'Connor, this was the first time so many horses had died at the same time.
"Everybody is kind of in shock and trying to figure out what happened," the Sun-Sentinel quoted O'Connor as saying. "Nobody can recall an incident in which this many horses have died at once."
The horses were between 10 and 11 years old and worth around $100,000 each, according to O'Connor.
The tournament is the 105th U.S. Open, the country's oldest and most prestigious polo competition. A meeting will be held to determine whether Lechuza Caracas will compete at a later date.
