Stephen Gately had an undetected heart condition which killed him, his family believes.
A post mortem examination carried out on the 33-year-old Boyzone star - who died at his holiday home in Palma, Majorca on Saturday (10.10.09) - ruled he had died from a pulmonary oedema, a build up of fluid on the lungs, which is often connected to heart problems.
The singer's mother Margaret Gately told family friend, lawyer Gerald Kean: "As soon as I head he had died I knew it was a heart problem. It has lifted a huge burden off our family's shoulders."
Gerald added: "There is a heart condition on his dad Martin's side of the family. Stephen would have had no idea he had this condition."
After seeing several family members die of heart problems, Stephen's relatives will now undergo checks to see if they have any similar health conditions.
Medical experts confirmed the post mortem tests suggest he may have been a victim of Sudden Adult Death Syndrome (SADS), caused by an undetected heart condition.
Dr. Sanjay Sharma, consultant cardiologist at King's College hospital, London - a leading expert in SADS - said: "The fact they found waterlogged lungs in this young man suggests his heart failed suddenly. That is a heart attack.
"In young people like Stephen, the vast majority of heart attacks are due to either hereditary diseases affecting the heart muscle itself or an electrical fault of the heart.
"If I was a betting man I would say it was an electrical fault. The heart would go into a fatally fast rhythm. That would only need to happen for a couple of minutes to cause death. Often in these cases, the first symptom is death."
It had previously been speculated Stephen had died after choking on his own vomit after a night out with his husband Andy Cowley.
However, local officials have been keen to stress that alcohol was not a factor in his passing.
A court spokesman said: "Stephen's death had nothing to do with any alcohol he drank that night and it has nothing to do with drugs.
"I'm not saying Stephen didn't vomit but I can categorically state he did not choke on it."