Washington - A mysterious illness killed at least 21 polo horses that belonged to a Venezuelan racing team just hours before a major competition in Florida, two Florida newspapers reported online Monday.

The tragedy struck just before an event at the 105th US Open Polo Championship tournament in Wellington, Florida, on Sunday, which ends South Florida's winter polo season, the Palm Beach Daily News reported.

The horses were members of the Lechuza Caracas team of Venezuela, which has been playing in the event annually since 1999, the Daily News reported.

Team owner is Victor Vargas, a Venezuelan multimillionaire.