Police investigating the murders of two British tourists in Thailand have questioned two British brothers and detained 11 Burmese people.
Hannah Witheridge, 23, and David Miller, 24, were found dead on a beach on the island of Koh Tao on Monday.
Brothers Christopher and James Ware were prevented from leaving Thailand and are in "police care", but have not formally been named as suspects.
Officers said they had not been arrested but were with police.
They also said blood stains had been found on the clothes of some of the Burmese migrants who were being questioned. DNA test results are expected on Thursday.
Meanwhile, post-mortem examinations of the victims showed Ms Witheridge died from head wounds and Mr Miller from severe blows to the head and drowning.
Police said Mr Miller also suffered wounds on his hands, which indicated a struggle had taken place.
The British brothers being questioned, who are believed to be from Jersey, were stopped at Bangkok International Airport as they prepared to leave the country, BBC south-east Asia correspondent Jonathan Head said.
Christopher Ware was previously questioned on Monday shortly after the bodies were found but was then released. James Ware had already left Koh Tao so he was not questioned at that time.
Police earlier described the pair as "possible suspects".
Our correspondent said this term was used because declaring a suspect is an official judicial process in Thailand.
The UK Foreign Office said it was "aware of reports that the Thai police have spoken to British nationals" in connection with the case.
"The investigation is a matter for the Thai authorities," it said.
"We stand ready to provide consular assistance if required."
'Loving young woman'
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.
On Tuesday, police released CCTV footage which they said showed Mr Miller and Ms Witheridge shortly before their deaths.
Ms Witheridge's family described her as "a beautiful, intelligent, loving young woman who poured joy into the lives of all who knew her".
"She was selfless and caring and made each and every day that little bit more wonderful," they said in a statement.
"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."
In a statement, Mr Miller's family said: "David was an artist by temperament. He had a creative eye that he carried with him through life and in his degree.
"He was hard-working, 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."
Paul Muller, managing director of Consolidated Minerals, an Australian firm where Mr Miller had recently spent five weeks on work experience, said staff were "deeply saddened" by the death of the "enthusiastic, inquisitive, intelligent and outgoing young man".