An oil slick from an unknown source polluted the sea and beach at Samae San island, off Chon Buri province, on Monday but was cleaned up before the end of the day.
Residents reported traces of black sludge along 400-500 metres of the island’s beach and a thin oil film on the water's surface about 200-300 metres from the shoreline around dawn.
Residents also said they could smell fuel oil and alerted the Naval Special Warfare Command at Sattahip Naval Base, which supervises the area round the island, which is about eight kilometres southeast of Sattahip district, and the Marine and Coastal Resources Research and Development Centre for the eastern Gulf.
The research centre’s director, Suppawat Karnatileklarp, said a vessel was thought to have dumped the oil into the sea. Whether it was intentional or accidental was not known. An investigation was underway to find the culprit.
They were examining the extent of petroleum hydrocarbon contamination from water samples collected at the scene.
Navy personnel had helped staff clean up the area.
“The beach and the sea has been cleaned up and the situation has returned to normal,” Mr Suppawat added.