Police on the resort island of Koh Tao in southern Thailand have stepped up their hunt for the killer of Hannah Witheridge, from Hemsby, and her friend, David Miller, from Jersey.
It is believed that Thai police have questioned a British man in connection with the murder of the UK tourists and he has been asked by Thai police to stay in Koh Tao.
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The man is also believed to be the backpacker initially sought by police following the murders early on Monday, Police Colonel Kissana, deputy Thai police spokesman, said.
He was subjected to a physical examination including a DNA test.
Mr Kissana said the man had not been arrested but was questioned earlier today and asked to remain on the island while police await the results of the tests.
'Once we receive the physical examination report, including a DNA test, we will be able to determine if he was involved in the incident,' he said.
He added that six Burmese nationals arrested over the incident after raids on their accommodation yesterday remain in police custody and have also undergone DNA testing.
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.
A spokesman for the British Embassy in Bangkok, which released a statement yesterday saying they had no information to suggest any British national is a suspect in the investigation, confirmed that this is still the case.
He added: 'The investigation is a matter for the Thai authorities.'
British consular officials from the Thai capital Bangkok have travelled to the island to liaise with local officials.
Officers have also released still images from surveillance cameras in the area. One showed what police said were the two victims walking together hand-in-hand.
Officers said a man pictured in a later image, who looked Asian, was considered a prime suspect, but they added they are following a number of leads in the case.
'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.'
It was not thought the victims were a couple, but had met recently on the island.
Their bodies were found on a rocky section of the shore around 100 yards from the scene of a beach party.
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