James Gandolfini's autopsy report will confirm he died of a heart attack.

A source at the Umberto I hospital, where he was admitted, has revealed the investigation into his death has concluded the 51-year-old actor died of natural causes in Italy on Wednesday (19.06.13).

Gandolfini had planned a ''guys' trip'' to spend time with his 13-year-old son Michael - his child with ex-wife Marcy Wudarski - and was due to participate in the 59th Taormina Film Festival in Sicily with Italian director Gabriele Muccino, when his son found him lying on the floor in his hotel room and alerted staff.

According to Claudio Modini - the head at the hospital emergency room - doctors and nurses tried to resuscitate Gandolfini for 40 minutes before pronouncing him dead.

The three-time Emmy Award winner first found fame in 1992 when he landed a role in a Broadway version of 'A Streetcar Named Desire' alongside Alec Baldwin and Jessica Lange, shortly afterwards he played a hitman in the 1993 movie 'True Romance' but he shot to fame as Mafia gangster Tony Soprano in TV series 'The Sopranos'.

Some of the most poignant tributes have come from his co-stars in 'The Sopranos' in the wake of his passing.

Edie Falco - who played Carmela Soprano, the wife of Gandolfini's character Tony - admitted she was ''shocked and devastated'' by his passing.

She added: ''He was a man of tremendous depth and sensitivity, with a kindness and generosity beyond words. I consider myself very lucky to have spent 10 years as his close colleague.''