Stephen Gately, the gay Boyzone singer who died on holiday in October, was killed by an undiagnosed heart condition, a forensic report has said.

He suffered from atheromatosis, which is a thickening of the arteries. A preliminary pathology report said the star died from an acute pulmonary oedema, a build-up of fluid on the lungs caused by the atheromatosis.

The report made it clear he had not been killed by alcohol or drugs.

Atheromatosis is considered rare in people aged under 50. It causes fatty deposits to line arteries leading into the heart, until the heart cannot pump blood around the body.

Gately’s mother suggested after his death he may have been killed by a heart condition, saying a number of relatives had suffered similar health problems.

It was also revealed that the star died up to eight hours before his civil partner Andrew Cowles realised he was not breathing.

The couple were on holiday in Majorca when Gately died.

Last month, Georgi Dochev, the Bulgarian student who was with the couple that night, sold his story to a newspaper.

Dochev told the Sunday Mirror that he and Cowles had slept together in the bedroom, believing that Gately was sleeping off a hangover.

He said: “It wasn’t sleazy. It was three consenting adults.”

Dochev also claimed he and Cowles had an “unbreakable bond”, although Cowles reportedly will have nothing to do with him.

Boyzone’s management refused to comment on the claims.