UPDATED 4.45pm: Coastguard is investigating a report of a capsized vessel seen in the water near Mayor Island.
A Wahi Beach Volunteer Coastguard crew has reached the boat which is about two nautical miles or 3.7km south of Mayor Island.
The white, upturned hull of a boat about 5-6 metres in length was reported by a light aircraft after 3pm.
Coastguard Eastern Region operations manager Stuart Lowth says the Waihi Beach crew are trying to establish a drift pattern to see where the boat may have come from, and where any people may also be drifting.
No one has been sighted in relation to the boat.
"We are doing some preliminary work on setting a drift pattern, so we can ascertain the drift of the vessel and any possible persons in the water.
"We have nothing further to report at this stage."
An all stations call directed a boat that was already fishing out at the island to the scene. No people have been reported in the water.