A spill from a fuel pipeline into Tauranga Harbour two months ago cost oil company Mobil almost $700,000 to clean up.
About 1500 litres of oil was spilt as a ship was being refuelled in April.
The Bay of Plenty Regional Council said it had finished cleaning the worst affected areas of Matakana, Rangiwaea Island, Pilot Bay and Sandy Bay.
But it said, rather than working to a deadline, the cleanup would continue until all areas have reached an acceptable end state rather than an end date.
The council has invoiced Mobil for $691,766 in clean-up costs.