Police have released footage of missing 10-year-old boy Alex Fisher with his brother Eric from CCTV images captured on Monday evening.
The footage was captured at Waitarere Four Square.
Police plan to resume the search for Alex tomorrow morning.
Inspector Sarah Stewart said the public could help by reporting any sightings of Alex and his adult brother from Monday. She said with each passing hour, police grew more worried for Alex.
Alex's family have released a statement.
"We would like to thank all those involved in the search for our son, brother and cherished family member."
"We appreciate the efforts and support from friends, family members and the public," the family added.
"At this time we request that our privacy is respected at this difficult time."
Earlier, police found the missing boy's asthma inhaler and his pencil case.
Manawatu Area Commander Inspector Sarah Stewart said police were concerned for Alex's health after finding the inhaler, but there was still no evidence of foul play.
"Obviously for us the concern is growing...as the hours go by we're growing more and more concerned for his safety," Inspector Stewart said.
Alex, 10 has been missing for more than 24 hours. He went missing from a domain near the southern block of the Waitarere forest, north west of Levin, sometime early on Tuesday morning. He had been with a family member before becoming separated, police said.
Ms Stewart revealed police got the call from Alex's family at 4am yesterday.
She said the last known CCTV footage of him was from 6.30pm on Monday.
Ms Stewart would not be drawn on who the family member with Alex was or any other details about that.
Media are now being taken into the forest with searchers.
The rescue operation is focussed on the South Block forest, which is where Alex was last seen.
The search area in South Block includes areas of dense undergrowth.
A series of interlinked dirt roads passed through South Block.
Another area where search teams were looking for Alex included roads recommended only for four-wheel-drive vehicles.
Parts of the search area were dominated by big tall trees, lots of bushes, and lots of branches on the ground.
Incident controller Sgt Bill Nicholson said there were no plans to keep searching for Alex overnight.
Mr Nicholson said about 80 per cent if South Block had already been searched.
The items belonging to Alex - including the inhaler and pencil case - were all found close together.
Sgt Nicholson said once the remaining part of South Block was searched, police would reassess the search.
The nearby beach was also searched today.
The Phillips Rescue Helicopter was also involved, and thermal imaging technology was used.
Mr Nicholson said it was unclear how long the search would continue "but at this stage, we will be searching tomorrow."
Horowhenua mayor Brendan Duffy said it was still a "search and rescue" mission and the community needed to be vigilant.
At least 55 people were involved in searches this morning.
Mr Duffy thanked the Waitarere community for support given to searchers today.
Apart from police, land search and rescue teams and the air force, a team from Palmerston North District Council was expected to join the operation soon.
Police have asked Waitarere locals to check their properties and garages, but to stay out of the forest and domain areas.
Asked if anybody had been arrested after Alex disappeared, Inspector Stewart declined to comment.
She also said police were unaware of any health problems Alex had, other than asthma.
A Royal New Zealand Air Force helicopter has been drafted in to help in the search.
The air force chopper, from the Ohakea base, joined a police helicopter fitted with infrared technology, which hit the skies at daybreak this morning to continue scouring the Waitarere Forest and surrounding areas.
A police spokesman in Levin said Air Force personnel from Ohakea were involved in the search.
A white helicopter seen in the area was not an Air Force machine but belonged to the local Westpac Rescue helicopter trust.
The helicopter this morning landed in a paddock and police stepping out of the chopper said the latest search turned up "nothing of interest".
The search for Alex has drawn many local volunteers to the Volunteer Fire Brigade station on Forest Rd.
Alex's father is also helping with the search.
Maureen and Keith Smithson and their friend Nook Yule walked to the station to volunteer.
The Smithsons, from Paraparaumu, and Mr Yule, from Feilding, were all in Waitarere on holiday.
Locals have been baking for the search team and bringing it to the Fire Station.
A Civil Defence van this morning arrived at the end of Forest Rd, near the forest block where searchers on foot are looking for Alex.
It's understood at least three of Alex's family members were in Waitarere this morning and were in a distraught state.
More than 50 searchers spent the night scouring the forest's rugged terrain for the missing child, who suffers from asthma. It was not known whether he had his inhaler with him.
Search and rescue volunteers from Taihape, Wanganui, Horowhenua, Palmerston North, Wellington and Ohakea were out searching for him.
Extra police teams from Wellington and Whanganui with dog units had been brought into the area this morning to help find Alex, police said in a statement.
Barry Fitzgerald, Scout leader at St Mary's Scout Group, Levin, which Alex attends, said he had received "a lot of calls" from members wanting to help find the boy.
"We're not helping with the search at the moment because it's not open to the public to assist. It's all done through the helicopters and police dogs etc, the search and rescue team. We just have to sit back and wait like everybody else."
It was pretty hard to take a back seat in the search, he said.
"I've had a few phone calls from Scout members, all asking the same thing, 'What can we do?' But we can't do anything at this stage. Everything's really just up in the air."
He added: "Everyone who knows Alex is obviously worried and concerned for him. I'm getting a lot of calls, as you do."
However, it was a matter of "waiting for the phone call" from police, Mr Fitzgerald said.
He did not want to comment on how capable Alex would be to look after himself in the bush, after police earlier pointed to his Scout experience and described him as a "sensible" boy.
"I haven't done a great lot of experience with him, he's only a young boy in Scouts. It's not as though he's had years of being in Scouting, a long time to learn a lot of skills. He's still only 10 years' old."
Ten is the starting age for Scouts.
At a press conference held this morning at the scene, Manawatu area commander Inspector Sarah Stewart said while Alex had been in out in the open for two nights, he was a boy scout and knew how to look after himself.
"He is sensible, a sensible young man."
The search had been difficult, she said.
"They have been searching what is a very difficult search area with very tight undergrowth," she said.
The forest was large and rugged with a lot of "dense" scrub in places.
"We are working hard to find him."
The plan today was to research areas of interest, Mrs Stewart said.
The family were staying away from the search area at this stage.
"It is an incredible difficult time for the family. They are being as helpful as they can ... It's really tough for them."
She called on people who have properties at Waitarere Beach or near the forest to check their properties for any sign of Alex.
"We ask that people search properties and make sure make sure Alex isn't there."
Last night a police spokeswoman confirmed "items thought to have belonged to the boy have been collected by police".
Ms Steward said: "There have been a small number of items that we know belong to him which have helped us in focusing our search."
However, other items were still being examined to see if they belonged to the boy.
"It's a well used part of the forest," she said.
Meanwhile, the young scout is believed to be wearing clothing which will help keep in warm.
"He is wearing a puffer jacket, has a sweatshirt and grey track pants on."
Alex has brown hair, is 1.52m tall and was wearing a red hooded sweat shirt, blue shorts and black shoes.
Police and search and rescue teams with dog units searched the forest and beach areas yesterday for Alex and rescuers asked the public to stay away while the dogs work to find tracks in the area.
Hydrabad Holiday Park and Waitarere Beach Motor Camp owner Deborah Nichol told the Herald police helicopters were at work and one landed across the road from the motor camp earlier.
"The place is crawling with cops and LandSAR guys."
The southern block of the forest was about 15sq km, she said.
"It's not huge. Roughly we're looking at between 4.5km and 5km from the southern entrance to Hokio Beach and then it's about 3km or 4km wide."
Mrs Nichol found out about the search mid-morning after campers were stopped by police in the domain, just behind the camp.
Earlier in the day, officers were showing people in the area photographs of Alex.
He's the first person to go missing in the area since a man was lost in the forest's larger northern block "donkey's years ago", Mrs Nichol said.
A Waitarere resident, who asked not to be named, said the domain area where the boy was last seen was a busy hang-out for children and families during the day.
There weren't any camping facilities there, but there was a BBQ area.
"The domain is our main playground for our children. It's got a Scout hall, a field, tennis courts there, that sort of thing. It's a popular area."
Tony Strawbridge, who runs the Windy Waves Bed and Breakfast, said the temperature in the seaside town was about 15C or 16C yesterday.
The southern block of forest, where the search was concentrated, was a fenced area with cycle tracks.
"It would be very hard to get lost in there," he said.
"As locals we've been asked just to keep out of the forest. They've got a helicopter I've seen going up and [the searchers] are using the local fire station as a base."
Local MP Nathan Guy said Waitarere Beach was a close-knit community of about 500 people and many of them were looking for Alex.
"This has sent shockwaves through a very small community."
Mr Guy said Alex "could be anywhere" but searchers were doing everything possible to find him.
He said two local forest blocks were popular with people running, walking their dogs, and mountain biking.
The bigger forest block extended to the Manawatu River mouth.
Mr Guy said the local search and rescue operation was unprecedented.
A private helicopter has been seen scouring the coast and a private sniffer dog company was also involved.
He said any parents would be able to sympathise with Alex's family right now.
"It's very traumatic for them."
- additional reporting: John Weekes of NZME News Service