Petronas said it had shut down pipelines at an oil platform off Malaysia’s east coast after discovering an oil sheen near facilities it shared with other contractors.

“The contractors have cleaned up the majority of the sheen and are now monitoring the situation via aerial and marine surveillance,” Petronas said in a statement. Petronas said it was still trying to identify the source of the sheen.

The facilities are operated by Petronas Carigali — the company’s exploration arm — and its production-sharing contractors ExxonMobil, Production Malaysia and Newfield Peninsular Malaysia.

An industry source said the oil sheen was first spotted on July 6.

“We don’t know where the oil is coming from,” the source said. “We don’t know which pipeline it is. All...have stopped pumping. Spraying has stopped now and will resume tomorrow.”

Emergency response and oil spill teams had also been sent to the area, Petronas said. Petronas did not say which oilfields were affected. Oil and gas fields including Tapis, Seligi, Guntong, Semangkok, Irong Barat, Tabu and Palas are situated off Malaysia’s east coast.

Last week, Petronas said Malaysia’s crude oil output had fallen 3.3 per cent to 535,000 barrels a day.