BANGKOK (AP) — Two migrant workers from Myanmar pleaded innocent Monday to charges that they killed two British tourists on the Thai resort island of Koh Tao, brutal slayings that raised concerns about both tourist safety and police conduct in Thailand.

Nakorn Chompoochart, the lawyer for the two men, said they made their pleas in a court on nearby Samui island.

The bodies of David Miller, 24, and Hannah Witheridge, 23, were found Sept. 15 on a beach on Koh Tao, a popular island in southern Thailand. Autopsies showed both had suffered severe head wounds and that Witheridge had been raped.

Win Zaw Htun and Zaw Lin, both 21, were indicted Thursday on several charges related to the slayings.

They say confessions that they have since retracted were extracted through beatings and threats, which police deny. The trial's first hearing is scheduled for Feb. 25.

Investigating police faced a variety of criticism, starting with their failure to secure the crime scene and releasing several names and pictures of suspects who turned out to be innocent. After Britain's Foreign Office expressed concern to Thai authorities about the way the investigation was conducted, British police were allowed to observe the case assembled by their Thai counterparts.

The gruesome killings tarnished the image of Thailand's tourism industry, which has been struggling to recover since the army staged a coup and imposed martial law in May.