Two Burmese men suspected of killing a pair of British tourists on the Thai resort island of Koh Tao have retracted their confessions and now say they did not see what happened, their lawyers said Tuesday.

The battered bodies of Hannah Witheridge and David Miller were found Sept. 15 on a beach on Koh Tao island.

The two suspects, Zaw Lin and Win Zaw Htun, say they did not commit the murders, their lawyers told the BBC.

Thailand's National Human Rights Commission said Monday that it had found evidence that both men were physically abused by police.

The suspects have been charged with conspiracy to murder, conspiracy to rape, and robbery, and are facing the death penalty if proven guilty.

Post-mortem exams uncovered that Miller died from drowning and a blow to the head, while Witheridge died from head wounds, the BBC reports.

London's police force said Scotland Yard detectives will travel to Thailand to help with the investigation into the killings.

Police said in a statement Saturday that officers would work with Thai police "in ensuring that whoever murdered Miller and Witheridge is brought to justice in a fair and transparent way."

Last week the British government summoned a senior Thai diplomat to express concern about the way the investigation had been handled.

The British delegation follows talks this week between Prime Minister David Cameron and Thai leader Prayuth Chan-ocha.

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The Associated Press contributed to this report.