Swansea striker Idrizaj dies
"It is understood (he) died in his sleep on Friday night while at home with his family in Austria," the club said on their website.
"The exact cause of death has not been confirmed and our thoughts are with his family, friends and team-mates at this time."
Swansea signed the former Liverpool forward and Austrian Young Player of the Year on a two-year deal in August 2009.
In February 2008, during a loan spell at Wacker Innsbruck, Idrizaj collapsed on the pitch during an Austrian top-flight fixture.
It was first thought he had suffered a heart attack but the problem was later diagnosed as a virus, Swansea said on their website.