Image copyright Facebook Image caption The pair were found close to the bungalows where they had been staying

Police investigating the deaths of two Britons in Thailand say they are looking for a number of suspects - but have ruled out other British tourists.

Thai police previously said they were looking for a British friend of David Miller, 24, and Hannah Witheridge, 23.

The pair were found dead on a beach in Koh Tao on Monday, having suffered serious injuries in an attack.

Police said they were now focussing their investigation on the Burmese migrant worker community on the island.

Mr Miller, from Jersey, and Ms Witheridge, from Hemsby in Norfolk, were found close to the beach-side bungalows where they had been staying.

A garden hoe believed to have been used in the attack was found nearby.

The bodies have been taken to the capital, Bangkok, for forensic analysis and are expected to be returned to their families after that.

Media playback is unsupported on your device Media caption The BBC's Jonathan Head: ''A veil of sorrow hangs over this island''

BBC south-east Asia correspondent Jonathan Head said the police's focus on Burmese migrants would be "quite controversial" as Burmese people were "often scapegoated" for crimes in Thailand.

He said police reinforcements had arrived on the island to help with the investigation, along with a consular official from the British Embassy.

Police still want to speak to a British man who was with the victims on Sunday evening, but the man is probably not a "major suspect", our correspondent added.

"They simply want to question him because they believe he was with David Miller and Hannah Witheridge as part of their group and then left early [on Monday] morning," he said.

Police said they had CCTV of Mr Miller and Ms Witheridge walking together, and later footage showing a man - described as being of Asian appearance - who is now the prime suspect.

Image copyright Royal Thailand Police Image caption Thai police believe they have CCTV showing David Miller and Hannah Witheridge before their deaths

Image copyright Royal Thailand Police Image caption Officers say a man of Asian appearance, pictured by CCTV, is their prime suspect

"We are focusing on migrant workers because of the surrounding witnesses and evidence, including the video footage," Major General Kiattipong Khawsamang said.

"We are sweeping hotels, bars, businesses and residences of migrant workers on the beach to find the suspect."

At the scene

Image copyright EPA Image caption Police cordoned off the scene and extra officers have been called in from elsewhere in Thailand

By Jonathan Head, BBC south-east Asia correspondent

The shocking death of the two young tourists has cast a pall over this scenic island resort

Locals say they can remember nothing like it happening before.

The police say they are focussing their investigation on Burmese migrant workers on the island.

One senior officer told the BBC he did not believe a Thai person could have committed such a crime.

Police say they have examined CCTV footage showing the two victims leaving a bar late on Sunday night, towards the beach - but they were killed in a hidden spot behind some rocks, and no eyewitnesses have yet been found.

A consular official from the British Embassy has arrived on the island to co-ordinate with the police, and offer help to any friends of the victims who are still here.

Alun Watkins, headmaster of Victoria College in Jersey, where Mr Miller was a pupil, said his death had come as a "real shock".

"He was a bright young man and a talented artist, with real potential to forge a worthwhile and fruitful path in his life," he said.

"It is hard to comprehend how that life can have been brought to such a cruel and abrupt end."

Writing about Mr Miller on Facebook, Bianca Moya-Vidal posted: "In shock. So glad I had the pleasure of knowing you. You were crazy, hilarious, witty and intelligent all at the same time."

Tony Reeve, a friend of Ms Witheridge's family, said: "This should have been a holiday of a lifetime for her and ended in her losing her life."

In a Facebook post about Ms Witheridge, Sarah Bird wrote: "Such a beautiful, funny girl with such a bright future. It was a pleasure to have known you. Thinking of your family and friends at such a horrific time."

Koh Tao

Small island covering eight sq miles (21 sq km) north of Koh Samui and Koh Phangan in Gulf of Thailand

Population of about 2,100 and visited by between 400,000 and 500,000 travellers per year

Popular with backpackers and divers

Quieter and less developed than neighbouring islands which are known for nightlife and beach parties

Thailand attracts more than 850,000 British and Irish tourists each year, and the UK Foreign Office says 11 British nationals have been murdered in the country since January 2009.

It warns that Western tourists have been victims of "vicious, unprovoked attacks by gangs" on the nearby island of Koh Phangan, but there are no specific warnings for Koh Tao, which is a popular tourist destination.

The Tourism Authority of Thailand said Koh Tao and other beach destinations in Thailand remained safe for tourists.

The country's Prime Minister, General Prayuth Chan-ocha, said: "This should not have happened in Thailand. It will affect our image in the eyes of international countries."