Fire and Emergency have discovered that it is a power cable - not a fuel pipe - which has caused a diesel leak in South Auckland on Monday.
Three crews have been at the scene on Great South Road in the suburb of Manurewa since 6.30am this morning.
Northpower helped Fire and Emergency to establish that it was a power cable with fuel insulation around it in order to cool it down.
FENZ assistant commander Chris Delfos said there would be some ecological damage to the waterway as a result of the leak.
It will be working with Auckland Council to mitigate as much of that as possible.
Earlier, Delfos told the New Zealand Herald that it appeared there had been some sort of "sabotage" to the pipeline.
In a later press conference, Delfos said the damage was "possibly" intentional.
Firefighters were working to prevent any further fuel loss, but the quantity of fuel involved was unknown.
A worker was earlier seen emptying buckets into a large yellow container.
A lane on busy Great South Road was closed with traffic being moved around it.
