Mobil estimates about 1500 litres of fuel has been leaked into Tauranga Harbour this week and the oil has now reached Pilot Bay.
The fuel oil leaked into the harbour on Monday during a ship bunkering operation, from two corrosion holes about 4mm wide in a 150mm wide lateral pipeline.
Mobil Oil New Zealand Country Manager Andrew McNaught said, "While it is difficult to make an accurate assessment of the volume lost given the circumstances, Mobil estimates the volume of fuel leaked into the Harbour to be approximately 1500 litres."
"The pipeline system to the wharf has been shut down until inspections and testing can be done on all sections of the pipeline branches along the wharf to ensure their ongoing integrity.
"The investigation is continuing and the priority is to understand how this failure occurred. Further metallurgical testing of the pipe will be required to understand the specific cause, and this will take some weeks," he said.