The 31-year-old was found dead at the team's hotel this morning, ahead of Fiorentina's Serie A clash with Udinese on Sunday.
The Italian outfit initially said that the cause of death was still unknown, but Udine prosecutor Antonio De Nicolo has now revealed that it was due to a suspected cardiac arrest.
"The idea we have of the situation is that the player died of cardiac arrest by natural causes," De Nicolo is quoted as saying by The Mirror.
"It is strange that such a thing should happen to a professional who is so closely monitored and showed no warning signs."
All Serie A games were subsequently cancelled on Sunday.