Thai police called in over 30 fishermen to take DNA samples as they expanded an investigation into the murder of two British tourists on a southern island, local reports said Monday.
Police also said they had detained two men who were seen on CCTV at the time and around the area of the murders, Thairath newspaper reported.
Police had earlier questioned migrant workers and a travelling companion of the murdered man, before DNA testing cleared them of involvement.
The murdered tourists, one man and woman, were found on the beach last week at the island resort of Koh Tao, 350 kilometres south of Bangkok.
The couple, both 24, suffered extensive injuries to the head and neck.
In the past five years, 13 British tourists have been murdered in Thailand, out of the more than 4 million who visited the country.