British police who travelled to Thailand to review the investigation into the murders of backpackers Hannah Witheridge and David Miller are due to return to the UK, having completed their work "as far as possible".
Metropolitan Police officers flew out to the Thai island of Koh Tao last month to work with the Royal Thai Police after an agreement between David Cameron and military ruler General Prayuth Chan-ocha.
It followed international concern about the way the case has been handled by the Thai authorities.
Mr Miller, 24, from Jersey, and 23-year-old Ms Witheridge, from Great Yarmouth in Norfolk, were found dead on a beach in September.
Scotland Yard said the British officers will compile a report from their review.
Police in Thailand are offering a reward of more than £13,000 to try to catch the killers of two British tourists.
David Miller, a Leeds University student, and fellow traveller Hannah Witheridge were murdered in Thailand. Their bodies were discovered on a beach on the island of Koh Tao on September 15th.
A group of footballers have been questioned by detectives investigating the brutal murders.
A bloodstained garden hoe, believed to be the murder weapon, was found nearby.
A spokesman for the Royal Thai Police confirmed that DNA samples were taken from "more than eight" footballers - who reportedly threw a late-night party at the nightclub where the victims spent their final hours - and officers were awaiting the results.
Police colonel Kissana Phathanacharoen said a reward of 700,000 baht is now being offered for information which leads to the arrests of those responsible.
"We are working around the clock. We are trying to narrow our inquiries and collect more evidence. We are encouraging the public who many have information to come forward.
"We are checking DNA but this is not the only thing we are looking at to prosecute the suspects."
Media reports in Thailand claim police are almost ready to arrest and charge more than one suspect over the murders of former Leeds University student David Miller and fellow backpacker Hannah Witheredge.
The Broadcast outfit Thai PBS quotes Southern police chief Pol Lt-Gen Panya Mamen as saying police have now gained enough evidence to arrest more than one person over the murder of the two British tourists in Koh Tao.
He is said to have "expressed confidence' that they will be arrested and charged within this week.
It's also reported that police have dismissed news report that the tourists might have been killed by local mafias after having heated argument with them. And that two suspects who were speed boat employees had been cleared after DNA testing did not match that found at the scene and on one of the bodies.
Police investigating the murder of former Leeds University student David Miller and fellow backpacker Hannah Witheridge have released the 12 suspects after DNA samples collected from the victims and the scene do not match any of them.
"We still believe we will bring the attackers to justice.
"Police have collected a lot of evidence and interviewed many people, and this should help us find the culprits.
"There is a lot of evidential information that we cannot reveal to the media right now.
"Sadly, the clues revealed so far have proved to be blank and the suspects have been released.
"From the available evidence, we believe that there were more than two attackers. "I am well aware that the murders have affected Thailand's reputation and travellers' confidence. I'm asking for more time as I want to work on a step-by-step basis,"
There have been harrowing scenes in Thailand as the distraught parents of one of the two murdered backpackers arrived in the country as local police admitted they have no idea who the killer is.
It's four days since Leeds University student David Miller and Hannah Witheridge were found battered to death on a beach on the island of Koh Tao.
Today Hannah's family hugged each other in front of the cameras as Thai Police revealed they had no DNA match to any of the 12 suspects they've been questioning. Jon Hill reports.
Police in Thailand say they have no idea who murdered the Leeds University student David Miller, 24, and fellow backpacker Hannah Witheridge.
The holidaymakers were found bludgeoned to death on the island of Koh Tao in the early hours of Monday.
Today Police said DNA results ruled out 12 of their suspects. And two British brothers - friends of David from Jersey - have now satisfied the authorities they had nothing to do with the killings.
23-year-old Hannah's distraught family today attended a joint police and British Embassy press conference in Bangkok.
Police hunting the killers of two British backpackers have carried out a number of raids on the Thai island where the pair were found murdered.
Hannah Witheridge and David Miller were discovered on a beach on Koh Tao on Monday.
Four more men are believed to have been questioned in connection with the deaths following the raids.
DNA tests have found no matches to link the two British backpackers to earlier suspects detained by Thai police.
The distraught family of murdered British backpacker Hannah Witheridge have arrived in Thailand
Relatives of the 23-year-old hugged each other as they arrived at the headquarters of the Royal Thai Police in Bangkok.
Officers have so far failed to match her DNA with any of their suspects.
Her body was found alongside fellow Briton David Miller, 24,on the island of Koh Tao on Monday. Post mortem tests have showed the pair died from head injuries.
Tests carried out on eleven Burmese migrants questioned over the murders of British backpackers David Miller and Hannah Witheridge have shown no DNA matches, Thai Police have said.
The group were arrested after bloodstains were found on some of their clothing.
Two British backpackers found murdered on a Thai beach died from head wounds, tests have shown.
Post mortem tests carried out in Thailand found Hannah Witheridge died from head wounds while David Miller died from severe blows to the head and drowning.
Thai Police also revealed Mr Miller suffered wounds on his hand, indicating a struggle had taken place.
The pair were found murdered on a beach on the island of Koh Tao on Monday.