Alarming messages pleading for help are the last thing the family of missing 15-year-old LA Tukerangi heard from her.

LA urgently messaged her family on Saturday morning, saying she was being held against her will by 36-year-old career criminal Dean Wayne Whakatau, who has almost 50 prior convictions and has previously been charged with kidnapping and rape.

Police said they had "grave concerns" for the Auckland teenager.

A series of panicked messages written by LA to her 18-year-old sister have been released to NZME News Service today, in the family's latest emotional plea for her return.

The messages -- parts of which can not be published for legal reasons -- say LA was taken to Rotorua by her boyfriend's older brother, Whakatau.

The first message, sent in all-capitals at 10.58am, said: "Keysha iv been kidnapped call the cops im in Taupo please help me."

Asked what the message meant, LA replied: "Garrys older brother hea like 30 something he stole me I'm in rotarua ... please help."

She later said she was taken after a fight at her boyfriend's Clendon home, adding: "Quick get help I cant text you when. Hes with me ... please help call them hea back please."

When her sister asked LA for the address, LA replied: "I don't no it bye love you keep safe I'll steal the phone tomorrow in the morning bye sis miss you please get help rotarua :'( asap."

LA also messaged her mother Marie Tukerangi on Facebook, saying: "Mum, I've been kidnapped. Help me please".

That was the last the family had heard of her, Ms Tukerangi said.

The "heart-breaking" messages were the reason the family was frantically searching for LA, she said.

"From there on in, you just go into silent mode. You become numb," Ms Tukerangi said.

"We just want her home and safe. We just want her home, we want to know that we're going to see her again."

Police are continuing to investigate a number of possible sightings of LA and Whakatau.

The pair are believed to have been in Rotorua CBD on Sunday, and may have spent time in Taupo in the last two weeks.

The latest sighting Ms Tukerangi was aware of was in Wellsford, north of Auckland.

"We called the police straight away, and so they're looking into it," she said.

A police spokeswoman said a number of unconfirmed sightings have been reported.

"We have had a number of potential sightings reported from around the North Island," she said.

"All of these sightings are unconfirmed at this stage and we are following through on those reports. A number pre-date Sunday when Whakatau was seen in Rotorua.

"We are not going to discuss the detail of unconfirmed reports as there is a risk that publication of such reports may be interpreted as fact and this could be unhelpful to the investigation."

In April, Whakatau was sentenced to 18 months' imprisonment for two counts of burglary.

He has been convicted nearly 50 times for dishonesty offending and police said he was someone who "takes advantage of good-natured and trusting people".

In 2005 he went on the run from police after escaping a Rotorua police station cell where he was being held accused of rape and kidnapping.

A warrant is out for Whakatau's arrest for breach of release conditions and the public is warned not to approach him.

He is described as 1.7m tall, of solid build and missing two front teeth.

Police are urging Whakatau to drop LA outside a police station or in a public place, and for anyone who sees the pair to call police.

* If anyone sees LA and Whakatau they are asked to contact police immediately on 111. The public are asked not to try to approach them as this may cause them to flee.

* Anyone with any information that doesn't require an immediate response is asked to contact Rotorua Police on 07 348 0099, or anonymously contact Crimestoppers on 0800 555111.