After 19 days of searching police have suspended the ground search for missing autistic man Nigel Peterson.
It was a difficult decision for Rotorua police to make but Constable John Frederickson said they could not keep searching at random.
Helicopters, drones and people power have been used in the extensive search for 33-year-old Peterson but so far only a handful of credible sightings have been reported to police.
Searchers have worked long days, in the scorching heat, sometimes covering up to 40km a day.
Despite the hours Frederickson said he liked it when they were still looking, when it was a proactive search.
"It is a bit of a slow process where we are now.
"It's about working on the reported sightings, working through any new information and we will follow all of that through to its conclusion."
He said there had been a possible sighting of Peterson at BP in Waiotapu, but police were still working to confirm that.
"I have some grave concerns, absolutely," Frederickson said.
"If he has found water, he will still be in a very bad way at this point."
At this stage police don't know if Peterson is dead or alive.
"Unless we find a body, that would be the only defining factor," Frederickson said.
"We've got to be honest with the family as well, and that's had to be discussed.
"To go off the radar completely like that is pretty unusual."
Peterson has been with a fulltime caregiver since he was 20.
On the day he disappeared - November 17 - he got wind he was being temporarily moved from his flat because of a water cylinder issue.
Before caregivers were able to properly explain the situation, he got out of the car and walked off.
The caregiver walked after him, but found it hard to keep up so got back in her vehicle. She drove alongside him on Old Taupo Rd trying to talk him into getting back in the car.
Frederickson said there was nothing suspicious about the disappearance.
Since then there has been one confirmed sighting of Peterson at the Hemo Gorge roundabout at about 4pm the day he went missing.
Frederickson said the few credible sightings since then were all within a week of him going missing.
The investigation will remain ongoing for as long as police continue to receive information.
"The family are still optimistic," Frederickson said.
"When there are no more questions being asked or we stop receiving new information, only then will the search be complete."
Nigel Peterson's description
• 33 years old
• Slim, medium height
• Wearing a green T-shirt, light brown pants, brown sneakers and possibly a denim jacket
• Often wrings his hands and could be talking to himself
• Walks with an unusual gait and leans to the side as he moves
Any information can be given to Rotorua police on (07) 348 0099 or the anonymous Crimestoppers line on (0800 555 111)