Mr Anderson said the search had widened with police questioning people throughout the Waikato, Bay of Plenty and as far away as Auckland.
But he was not discounting the possibility that the offender could be a local.
"It has the appearance that the offender was familiar with the road network here...as to where the person could be that's anyone's guess."
Mr Anderson said the vehicle could be hidden locally and he asked people to be vigilant.
He said the eagle helicopter had been in use to help with the search for the vehicle.
"We had a lady call us the other day about a submerged blue vehicle," he said. "We tracked it down and it was not the vehicle...this is a difficult place to search."
Mr Anderson said the investigation was proving difficult and frustrating.
"There's no doubt about that, it's frustrating in the sense we haven't resolved it yet."
"We still think there's a number of opportunities for the public of the community of the greater North Island to help us resolve this."
He said police had spoken with Mr Taiaroa's family to learn more about his background.