The pipeline owned by Star Petroleum Refining Public Company started leaking late on Tuesday before being brought under control a day later.

The navy has led the cleanup and said an estimated 5,000 litres (1,321 gallons) of oil remained on the sea surface about 16.5 km offshore and was unlikely to reach the coast soon, as conditions were calm.

The estimated volume of oil leaked has been revised down substantially, from 160,000 litres (35,195 gallons) to 50,000 litres (13,209 gallons), industry minister Suriya Juangroongruangkit told reporters.

SPRC said it was working with authorities and experts to evaluate and monitor the impact of the leak on the environment, and determine the cause. Environment officials had earlier said there was limited damage caused.

(Reporting by Panarat Thepgumpanat and Panu Wongcha-um; Editing by Martin Petty)