A married couple who were subjected to a "violent and sustained" attack in their home died from stab wounds, the initial post mortem results have confirmed.
Patrick and Gillian Kettyle, who were in their 50s, were found dead at their Fetcham home in Surrey shortly after midnight on Thursday by a member of their family, believed to be one of their teenage children.
Their deaths sparked a police search for Lithuanian builder Viktoras Bruzas, 38, who was later found in Oxshott less than five miles from the murder scene and arrested on suspicion of murder.
Bruzas, from Walton-on-Thames, was known to the couple and was reportedly in a relationship with a secretary at Mr Kettyle's building firm.
He remains in police custody, Surrey Police said tonight.
The full results of the post mortems as well as formal identification of the couple are expected next week.
Detective Superintendent Nick May, from the Surrey and Sussex Major Crime Team, said they were killed in a "significant, violent and sustained" attack.
Detective Chief Inspector Mark Preston, from the Surrey and Sussex Major Crime Team, said after their murders: "This is a tragic incident which has shaken the close community in Fetcham.
"I would like to take this opportunity to thank everyone who assisted with the search of Viktoras Bruzas including members of the public and the media."
He added that he hopes the arrest "goes some way to reassure the public that we have been relentless in our efforts during this fast-moving and on-going investigation".
Prior to Bruzas' arrest, police had been liaising with both the National Crime Agency and Interpol who were in touch with the Lithuanian authorities.
Another man in his 30s who was arrested at a property in Walton-on-Thames in Surrey yesterday has been released on police bail while the investigation continues.
Officers were called to The Copse, a quiet street of detached houses in Fetcham, at around 12.30am on Thursday.