Missing 19-year-old Maia Johnston found safe after mum made ...

A 19-year-old who was missing in Upper Hutt has been found safe although she has several broken limbs.

Missing teenager Maia Johnston has been found injured, but alive, in the hills around Upper Hutt.

The 19-year-old went missing on Saturday night and was last seen leaving a family home in the suburb of Totara Park at about 8.30pm, during heavy rain.

Mum Amy Walsh told RNZ Maia was found by police search and rescue in the dense bushy hills behind Totara Park.

She has a broken leg, some broken ribs, and it seems she may have had a fall - but other than her physical injuries she was well, and "cracking jokes".

They were awaiting a special stretcher to come from Wellington Hospital, that emergency services would be able to use to carry Johnston out.

Walsh said she was in disbelief when the police told her her daughter had been found alive.

"I thought she was dead," she said.

A family friend Susan Stephenson said she was being helicoptered out, but did not know the nature of her injuries, or how she got to the location where she has been found.

"We were just co-ordinating the next steps because we've been having people come and go and we've got a whiteboard of where everyone is and we're just getting ready to do the next shift change sort of thing," Stevenson said.

"Police came in to let us know that she has been found, and she has been found alive. It was just ecstatic and we were hugging strangers, it was just amazing," Stevenson said.

Stevenson said Johnston was alive, but injured.

"She is injured and she was up in Cannon Point, so she must have had a had a little bit of an adventure....she has been injured, but she's OK and she's alive."

Emergency services jumped into action once she was found.

"Helicopters arrived, ambulances arrived. They can't get her out, they need to hoist her out, so they're doing that."

Stevenson said she did not know how Johnston got up on the hill, or the nature of her injuries.

She thanked everyone who helped with the rescue efforts and said the community and rescue teams had been incredible throughout the search efforts.

"We had people from all around the country searching for her and keeping an eye for her. We had people come from all parts of Wellington, all parts of New Zealand, from Hamilton, helping search.

"We had strangers coming to search, we had mums that thought it could have been their kids so they came out here.

"We've not had a time where there hasn't been somebody walking in the door saying: how can I help?

"And we've random people drop food in to keep the searches going, and just the public. The public have just been amazing." Stevenson said.

On Monday afternoon police confirmed Johnston had been found.

She was located in a remote area and was speaking with rescue staff, police said in a statement.

Their priority was to ensure she saw medical staff as soon as possible so she could be assessed.

Police thanked the Upper Hutt community for the way they rallied around search staff and the family.

The mother of Maia Johnston missing since Saturday earlier pleaded for her daughter to come home.

Her employer has also expressed relief at the news she has been found.

Seed Waikato chief executive Tania Pointon said the charity's staff and board were "so relieved that Maia has been found safe".

"Maia is a beloved and highly valued kaimahi at Seed Waikato. She is a passionate community contributor with a love for community, te aoo Maaori and manaakitanga for others.

"After her outstanding mahi in community running her first ever charity event for Dry July, she gained an internship for six weeks and then accepted a fulltime role at Seed Waikato as Kaiawhina, communications and relationships."

Pointon said Johnston often spoke about and lived by her values of whakapono, whakapapa and mana motuhake.

"She is currently on her reconnection haerenga and plants seeds for others. She always includes her whaanau and friends in any activity we do."

She said Johnston was a role model, leading events, and using her "gift as an incredible speaker and host".

"She has a gift for storytelling and amplifying the voices of our young people. Maia is vibrant, energetic and hard-working.

"We mihi to all of the community members who have been searching for and are so happy she has been found."

Police had set up a base at a local school as the search for Johnston continued.

Her mother, Amy Walsh, speaking at the search base on Monday made an emotional plea for her daughter's return.

"Please just come home, she said.

"If you are alive and well I don't care where you are, I don't care what decision you made, I don't care who you are with," she said.

"I just want to hear you made a dumb decision and got in someone's car. Please just come home if you are still alive."

Up to 70 people joined the search on Monday, managed by a volunteer coordinator from the base at Totara Park School.

Dozens of people turned up to speak with the coordinator and check a map of the local area before heading out.

The search was centered in the Totara Park area, which was surrounded by dense, bushy hills and Te Awa Kairangi, the Hutt River.

Police said they followed up a number of calls from the public after appeals for information.

On Monday afternoon police said they were asking anyone in the areas of Totara Park, Harcourt Park and Brown Owl check their properties including any outbuildings such as sheds or sleepouts to see if Maia might have gone in there.

They were continuing to ask those who live in those three areas to check any CCTV footage for sightings.

Johnston, her sister and brother, and some friends had travelled down from Hamilton, where they live, for an early family Christmas with Walsh.

It had been a happy day, Walsh said.

Johnston and her best friend Kerry had been to the park in the early evening and sat chatting on the doorstep when they returned, Walsh said.

"Maia said to Kerry about 8 o'clock, I just need some time by myself."

That was not unusual, Walsh said, and Johnston had not been upset.

"There was nothing out of character to need a bit of fresh air. So she's walked off with just a vape," Walsh said.

But after about half an hour, Kerry realised Johnston had left her phone behind, and went looking for her friend in the pouring rain. Another half hour later, about 9pm, Walsh got in the car to try to find what she thought would be "two wet girls" at the park - but only Kerry was there.

They have been searching ever since - Walsh had not stopped since midnight Sunday.

"I had to force myself to go home and get some sleep so I could function today, and that was the worst feeling in the world, going home without my daughter," she said.

Walsh was worried her daughter had hurt herself, and that she had left her phone at home intentionally.

"There is a really small chance that she may have hopped in a car with somebody going to a party. Just be with other people she doesn't know.

"If it was just me, I would say 100 percent that sounds on character, that she wouldn't think that I would get worried, she wouldn't notify her parents, that's normal.

"For her best friend to be at my house, worried about her whereabouts, I just find it impossible to believe that she would willingly go to a party or go for a drive or hitchhike somewhere knowing her best friend would be worried about her."

Walsh said she was "absolutely blown away" that so many strangers - hundreds, she said - had turned out to search for her daughter.

Johnston's father was flying down to join this search on Monday afternoon, and her grandmother had looked through Johnston's house in Hamilton, and asked neighbours to call if she returned home.

She described her daughter as an "amazing, beautiful person".

"She does struggle with mental health, but she is so, so determined to be more than her mental health and to not get her mental health get the better of her.

"It's not always an easy place inside her head, but she wants better."