The stud farm, which suffered similar problems last year, when six Lipizzaners died, said in a press release that the cause of the health problems had not been known yet but that a report on horses' treatment was being drafted.

"We want to say that we took blood and stomach contents samples from all horses, the same as was done with horses that had similar health problems last year," Lipica said.

Last year, six horses died or had to be put down due to colic, a stomach condition, in March and July 2011, but chemical and toxicological analyses into the cause of death indicated that fodder was not the reason they had died.

The stud farm also noted today that the two horses that died had been sent for pathological and morphological analyses, while samples of fodder that the horses had been fed and the bedding from their stalls would be analysed shortly.

"We expect that analyses will provide an answer as to what has caused the disease," the press release reads.