Prodan made 188 career appearances, most of which came for Romanian giants Steaua Bucharest. Prodan played 54 times for the Romanian national team and was part of the team that reached the 1994 World Cup quarter-finals.
The defender also had a spell at Atletico Madrid where he played 34 times, scoring four goals and had then went on to have an injury-plagued three years at Rangers, where he failed to make a single appearance for the club.
Dorin Chiotea, a close friend of Prodan and journalist, broke the news of his friend's death on social media.
"Daniel Prodan died a few hours ago of a heart attack," Chiotea wrote. "He was 44. I was a great friend and his premature end grieves me deeply. It's the worst exclusive news of my career.
"The tragedy occurred in the Romania player's house. The collapse was seen by his wife, Licinia, who called for help".