The ruptured pipeline that led to Auckland Airport's fuel crisis last month may have been damaged as long as three years ago.
Fuel supply along the 170 kilometre pipeline from Marsden Point to Auckland came to a halt in September.
The rupture severed the main pipeline link between Marsden Point Refinery and Auckland, forcing fuel to be trucked in to the city.
It's believed the damage was caused by a digger.
Airlines were required to cut their fuel use to 30 percent of normal use and multiple flights were cancelled.
A small number of petrol stations briefly ran out of 95 premium gas. A naval tanker was also brought in to ship fuel from Marsden Point to Auckland.
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At the time Refining NZ said the digger damage had rusted, and gradually eaten away at the pipe.
Northland Regional Council has now said that the digger that damaged the pipe may have been present on the property three years ago.
"Evidence [Northland Regional] Council has collected to date indicates a digger was on site in the area of the damaged pipeline about three years ago," a spokesperson said.
The identity of the digger driver remains a mystery, but the Northland Regional Council says it's following a "strong line of enquiry".