The unfinished waka's prow appears to be in the middle of the buried tree, with branches and tree truck extending to one end.

What is believed to be a partially complete waka has been uncovered during excavation work on a motorway project in Puhoi, north Auckland.

The discovery was made on April 16 near the Ōkahu inlet north of the Johnstone's Hill Tunnel on State Highway 1, the New Zealand Transport Agency (NZTA) said.

The waka is thought to be about 10 metres long and still connected to the trunk of a kauri tree.

Jay Boreham Archaeologist Sarah Phear works with her team to uncover one end of the unfinished waka which still has branches protruding from it.

"A digger identified a wooden object under the surface of the inlet," NZTA's Chris Hunt said.

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"The mud around the object was carefully removed exposing a large rectangular wooden object that extended across the excavation."

Crown/Māori Relations Minister Kelvin Davis said it was a "significant discovery" that would grow Kiwis' understanding of where and how waka were made.

"It reinforces traditional korero around the use of resources including waka forests, where particular trees were identified and nurtured for waka construction."

Hunt said work had ceased immediately and an onsite archaeologist was notified, along with iwi partners Hōkai Nuku.

Jay Boreham The waka was undamaged by the digger which uncovered it.

Project archaeologist Sarah Phear was excited at the find, which she believed was the first waka to be found still under construction.

It was not yet known how old the waka was, who it belonged to or how it came to be left in an unfinished state.

Phear and her team were still at the early stages of understanding what had been found, and it was slow going removing the mud encasing the waka.

NZTA Work to uncover the discovery is slow going with workers having to pump out water from incoming tides each day.

"We pump out the water because every day it re-floods with the tides."

But the water was also keeping it from drying out and collapsing, she said.

"It is very important to keep it wet and get it into a conservation tank as soon as we can.

NZTA The waka would need to be carefully preserved, as the wood would likely deteriorate when exposed to air, the NZTA said.

"At the northern end it is still very much a trunk and some branches and we have a point in the middle that we think would have been the prow, but it is still early stages at this point."

It was expected the object would be lifted into a storage container and taken to a new site to be examined more closely and preserved.

Ngāti Whātua's Glenn Wilcox was grateful the project's staff had been trained to spot items of archeological significance.

"Fifty years ago we would have just chopped it up and not even thought about," he said.

Wilcox said there was much excitement from all involved at the find.

"Especially an unfinished one because there is actually more to learn from how they did it."

But this was tempered with investigating and understanding why it was covered over before it was finished, he said.

"Did they bury it for a reason ... and should we put it back in the ground?"

But this was a conversation to be had after work was done to conserve the waka and stop it from turning to dust, Wilcox said.

The find would not delay the motorway project, and contractors would work on other sites while the waka was examined and moved.