The owner of a boat found capsized off Port Waikato is yet to come forward.
However, police don't believe there is anything sinister in the find.
Maritime police, Coastguard and the Eagle helicopter have been searching the area but are yet to find anyone after the boat was found upturned about 1.35pm on Monday.
A police spokesperson today said they were still trying to work out what happened.
"We don't know what has taken place but we do not believe there is anything sinister at this time.
"We are really keen to find out who owns the boat and if they are okay as our concern is their safety."
Inquiries are continuing and the Eagle helicopter is continuing to search the area.
Anyone who has information about the boat, named Parauroa, or its owner is asked to phone the police maritime unit on 0800 102 835.