A young dolphin was found dead on a beach on Koh Samui in Surat Thani on Friday night.
Staff of the Coco Palm Resort Hotel at the Mae Nam Beach alerted police of the dolphin carcass.
Police and officials of the Kusol Songkroh Koh Samui Foundation did not find any trace of injury when they checked the carcass.
The dolphin was one-metre-long and was about one-year old. It was believed to have died a day earlier.
Officials buried the carcass near the beach and informed the local fishery office.