An autopsy on the body of James Gandolfini, star of the US Emmy-winning series The Sopranos, yesterday confirmed that he died of a heart attack, a hospital source said.

The source, who asked not to be identified, said Gandolfini’s death late on Wednesday in a Rome hotel was the result of “natural causes, a heart attack”.

Gandolfini, 51, whose performance as Tony Soprano made him a household name and help usher in a new era of American television drama, was vacationing in Rome and had been scheduled to attend the closing of the Taormina Film Festival in Sicily today.

The actor’s 13-year-old son, Michael, found him collapsed in the bathroom of his Rome hotel room, Gandolfini’s manager, Mark Armstrong, said in an e-mail.

Claudio Modini, the emergency room chief, said on Thursday that doctors had tried to resuscitate Gandolfini for 40 minutes when he arrived at the hospital before declaring him dead.

“The resuscitation manoeuvres, including heart massage, etc, continued for 40 minutes and then, seeing no electric activity from the heart, this was interrupted and we declared James dead,” said Modini.

Tributes continued flowing in.

Brad Pitt, who appeared in three films with Gandolfini, called him “a ferocious actor” and said he was “gutted by this loss”.

Academy Award-winner Kathryn Bigelow, who directed Gandolfini in Zero Dark Thirty, said she was devastated by the news of his death.

“James was such an enormous talent, and an even greater spirit. I will be forever grateful for the privilege of working with him, and shall cherish his memories always,” she said in a statement.

Actress Edie Falco, who played Tony Soprano’s long-suffering wife, Carmela, in The Sopranos, said her co-star was a man of “tremendous depth and sensitivity.

“I consider myself very lucky to have spent 10 years as his close colleague,” she said.