PETALING JAYA: The four-hour disruption to the Sungai Selangor Phase 1,2, 3 and Rantau Panjang water treatment plants (WTP) that had caused 1,337 areas in Selangor and Kuala Lumpur to experience unscheduled water supply has been traced to an oil spill from heavy machinery said Selangor Environment, Green Technology, Science, Technology and Innovation and Consumer Affairs Committee chairman Hee Loy Sian.