WEST PALM BEACH, Fla. — A member of a Venezuelan-owned polo team says a supplement likely killed 21 horses before a match last weekend in Florida.

Juan Martin Nero, of Lechuza Polo, tells the Argentine newspaper La Nacion the horses were given a commonly used supplement known as Biodyl that contains a combination of vitamins and minerals.

Nero says the drug is often given to horses, but was likely tainted at a lab.

The horses began collapsing Sunday as they were unloaded from trailers before one of the sport's top championships at the International Polo Club Palm Beach.

Nero says five horses that did not get the supplement were OK.

Florida authorities have started a criminal investigation to see if the deaths were intentional or an accident.