"We immediately shut down our fueling operations at the wharf. We have identified the sheen was originating from a fuel pipe line, which was shut down straight away and is still currently shut down."
Ms Potts confirmed Mobil owned the pipe that leaked.
Ms Potts said yesterday's rough weather conditions had helped disperse the fuel.
"The priority is containing any remaining fuel oil on the water and cleaning up any impacts on the local environment."
Mobil is working with the Bay of Plenty Regional Council to assess the situation and respond as needed, Ms Potts said.
At this stage, Mobil had no idea of the volume of fuel that leaked into the harbour.
"We don't know what the cause [of the leak] was. There was a leak from the pipe line as far as we can tell. There will be a full investigation to understand why this happened."