The couple from north Wales found murdered in a villa in Spain were asphyxiated, an autopsy has shown.
Anthony and Linda O'Malley were looking for property
Linda O'Malley, 55, and her 42-year-old husband Anthony, went missing in September while on a two-week holiday to look for a retirement home.
On Tuesday, their bodies of the couple from Llangollen were found buried in the cellar of a house in Alcoy, a town 12 miles inland from the coastal resort of Benidorm.
The post-mortem also revealed Mrs O'Malley had been badly beaten before being strangled.
Mr O'Malley's body was found with a plastic bag over the head.
The couple, originally from Liverpool, had been the subject of a missing persons hunt for six months.
Two men thought to be of Venezuelan origin, aged 53 and 37, are being held after being questioned by a Spanish judge about the murders.
The autopsy findings conflict with alleged confessions made by the suspects who were reported to have said they had shot the couple.
The two men were arrested on Tuesday after the car they were driving was stopped and found to be the same one the O'Malleys had hired.
One of the men later took detectives to the villa where the bodies were buried.
The O'Malleys' bodies were found in this basement
Police said on Thursday the O'Malleys had been tricked by an advert placed by the alleged captors in the English-language paper Costa Blanca News offering a villa for sale.
The couple were kidnapped at the villa and Mr O'Malley was believed to have been taken regularly to cashpoints and forced to hand over large amounts of money while his wife was held captive.
It is thought the couple were held for up to 15 days before they died.
Efforts to establish the true identities of the arrested men are ongoing.
One of the men had used a least six different names while involved in criminal activities, according to police.
They have begun examining unsolved fraud cases in Spain after interrogating the men.
The older man has been formally accused of swindling a female police clerk in the southern city of Malaga.
It is alleged he took up to £20,000 from her bank account during a relationship which lasted several months in 1996.