Up to 30,000 litres of diesel has leaked from a tank at the Devonport Naval Base.
A fire service spokesman said the fuel was leaking form a 30,000L tank at the base.
"It appears to not have entered into any waterways or into the sea at this time," he said.
Emergency services were called to the scene at 12.30pm.
Captain Andrew Hayton, harbourmaster at Waitemata Harbour, said there was no danger of the diesel getting into the sea.
Auckland Council's compliance and resource consents manager Sefan Naude said the fire service and council staff had inspected the site and confirmed that a small amount of fuel was spilled on an area of scoria.
"There is no evidence that the spill went beyond the site into the environment or the sea," he said.
"The fire service is satisfied that the spill does not pose any risk and have withdrawn from the site. The council does not consider any further action is required at this stage."
The New Zealand Defence Force is yet to comment on the incident.