“We estimate that approximately 30-40 metric tonnes of slop, which is a mixture of oil and water, was leaked into the sea,” the company said in a statement, adding that it was working with all relevant authorities to manage the clean-up effort.

“There is no impact to Bukom operations or supply. The leak has been stopped and we are taking steps to clean up the oil which has spilled,” a Shell spokesman said in an email.

Shell Singapore in August shut one crude distillation unit (CDU) and other facilities at its refinery in Bukom for a scheduled overhaul.

The maintenance was expected to end in the first half of October.

The company sold its refinery and petrochemical plants in Singapore to a joint venture company between Indonesia petrochemicals producer Chandra Asri and major trading house Glencore in early May.

The transaction is expected to be completed by the end of 2024.

Earlier this year, beaches on Singapore’s Sentosa island were closed after an oil spill spread from a nearby shipping terminal to the tourist haven south of the city-state.