Tests carried out on two British men questioned after the deaths of David Miller and Hannah Witheridge in Thailand have shown no DNA matches, according to reports.
DNA found on the body of Miss Witheridge, who was discovered semi-naked alongside Mr Miller on a beach on the island of Koh Tao on Monday, is understood not to match that of brothers James and Christopher Ware.
Neither of the Wares was declared suspects in the investigation but had been interviewed and asked to remain on the island by Thai police.
The DNA results are also understood to show that semen samples found on Miss Witheridge's body are not a match for Mr Miller's.
The Royal Thai Police yesterday said they had found "strong evidence" in connection with the deaths of Mr Miller, 24, and Ms Witheridge, 23, with a spokesman adding that 11 Burmese migrants had been questioned over the deaths, after bloodstains were found on some of their clothes.
James and Christopher Ware are thought to have shared a room with Mr Miller in Thailand.
Police Colonel Kissana, deputy police spokesman, said yesterday: "We have strong evidence that led us to the Burmese suspects as bloodstains were found some of their clothes. We have got to do whatever it takes to obtain concrete evidence."
Meanwhile tests on the dead pair have revealed more about how they died.
Major General Pornchai Sutheerakune, head of the Thai Institute of Forensic Medicine, said post-mortem examinations had shown Miss Witheridge died from head wounds while Mr Miller died from severe blows to the head and drowning.
Mr Miller also suffered wounds on his hand, indicating a struggle had taken place, police said.
A bloodstained garden hoe, believed to be the murder weapon, was found nearby.
More than 70 Thai police have been questioning migrant workers and tourists on the island, visiting hotels, bars, homes and businesses as they search for the killer.
The families of both victims have paid tribute to them.
Ms Witheridge was described by her family as "a beautiful, intelligent, loving young woman who poured joy into the lives of all who knew her", while Mr Miller was a "hard-working, bright and conscientious" young man who would be "sorely, sorely missed".
In a statement, Ms Witheridge's family said: "She was selfless and caring and made each and every day that little bit more wonderful.
"Our family are utterly devastated and shocked by what has happened to our beautiful Hannah. To lose her in the way that we have is beyond comprehension.
"We are heartbroken and no words can possibly describe how we feel. As such, we would be extremely grateful to be left in peace while we come to terms with our loss."
Mr Miller's family said: "David was an artist by temperament, so talented. He had a creative eye that he carried with him through life and in his degree.
"He was hardworking, bright and conscientious, with everything to look forward to.
"David was very giving to his family and friends and we all adored him. He will be sorely, sorely missed."