Rome (CNN) — Autopsy results are expected Friday for "Sopranos" star James Gandolfini, who is thought to have had a heart attack while in Italy on a working vacation.
Gandolfini was taken to a Rome hospital Wednesday after falling ill at his hotel in the Italian capital.
After failed attempts to resuscitate him, his body was transferred to the morgue early Thursday.
By law, medical examiners in Italy are required to conduct a postmortem 24 hours after the body's arrival in the morgue, a hospital spokesman said.
Professor Claudio Modini, head of the emergency department where the actor was taken, said the cause of death was probably "myocardial infarction," or heart attack.
Doctors had not noted any suspicious factors, such as alcohol, on his medical report, Modini said.
Ambulance staff tried to resuscitate the actor at the hotel, and further efforts were made when he reached the emergency room, Modini said.
Though the cause of death is not confirmed, his managers also believe that a heart attack killed the man who portrayed a mob boss prone to keeling over from panic attacks in the HBO show, "The Sopranos."
Gandolfini was scheduled to receive an award at the Taormina Film Festival.
Reactions to his death
He was to arrive Friday in Taormina in Sicily, a quaint town packed with historical architecture and nestled between lush green hills and the azure waters of the Mediterranean Sea.
Before Italian authorities can release his remains for transport back to the United States, the U.S. Embassy in Rome must issue a death certificate.
'Sopranos' cast mourns Gandolfini
The U.S. Embassy said it was "deeply upset" by the news of the actor's death, but had not received any official confirmation from local authorities.
It said the family will get assistance from the embassy when it requests it.
Gandolfini experienced a medical emergency about 10 p.m. Wednesday in his room, said Michael Kobold, who described himself as a close family friend of the actor.
He gave more details of his final moments in a news conference Thursday at the Boscolo Exedra Rome Hotel, where the actor was staying.
"The hotel notified emergency crews who responded, and first aid was administered before Mr. Gandolfini was taken to the hospital, where he died of an apparent heart attack," he said.
Kobold said he'd known the actor from New Jersey for more than a decade and lived with him years ago.