It's still being investigated, but keen-eyed mount walkers are left scratching their heads as to how a small dumper truck ended up in the water behind the landmark on Tuesday afternoon.

A team from Tauranga City Council was in the process of reinstating displaced protective rocks by Cyclone Gabrielle, to prevent further erosion on the base track.

It was then at about 12.30pm on Tuesday, March 7, the dumper truck rolled off of Mauao into an 'inaccessible” spot, facing an incoming tide.

The vehicle was damaged, according to council general manager of community services, Barbara Dempsy, and had to be moved by helicopter due to the tricky position it ended up in.

A helicopter was called to the scene. Photo: Supplied.

'The driver was not on the machine at the time of the incident, but they have been assessed as a precaution,” says Barbara.

When asked if this restoration was part of an ongoing project, Barbara says the incident occurred 'during regular maintenance” of tracks and structures on the maunga.