The leak at the pipeline owned by Star Petroleum Refining Public Company Limited (SPRC) started late on Tuesday (January 25), southeast of the Map Ta Phut Industrial estate, a major petrochemical complex, said Atthapol Charoenchansa, director-general of the Pollution Control Department.
Attapol warned fishermen to steer clear of the area but said the oil spill should be contained before it reaches the coast.
He earlier said Koh Samet, a resort island off Rayong province popular with foreign tourists, could be impacted by Friday (January 28), but has since revised the threat level.
Sophon Thongdee, Director-General of the Department of Marine and Coastal Resource, told local broadcaster ThaiPBS the cleanup should conclude on Thursday (January 27) and there was no major damage to marine life or habitat.
SPRC in a statement said the leakage was under control, adding that the leakage had not impacted refinery operation. SPRC's stock price plunged as much as 8.6% in early morning trade after news of the oil spill.