The mother of missing Auckland woman Rae Portman said she was "grieving" her lost daughter and her unborn grandchild.

This morning Rebecca Norton pleaded for information on her daughter's June 20 disappearance and during her emotional request, revealed Portman was four months pregnant at the time.

Portman, who told her mother of her pregnancy a month earlier, travelled from Hamilton to Auckland and checked into the Mt Albert Motor Lodge - her last known whereabouts.

She then moved around Auckland visiting friends and returned to the motel that evening, but failed to check out the next day and left personal belongings behind.

The 33-year-old was reported missing by Norton on July 2.

Police since confirmed Portman, nicknamed "Bok", had links to the drug world.

Norton described Portman as an outgoing, popular woman who had a wide circle of friends, and though the pair "didn't live in each other's pockets" she said they were close.

"It's every mother's nightmare and it's a nightmare that's come true," she said.

"It's a bit like grieving, even though we don't know where she is."

Someone must have information and Norton begged for them to contact police.

"You can't just disappear, nobody disappears," she said. "There has to be a body in some form somewhere. You don't just vanish into thin air.

"I just ask for that person out there who knows where she is, to do the right thing."

Detective Inspector Mark Gutry, who is leading the investigation, said police had built up a timeline around when Portman went missing and they were positive about finding her.

A woman appeared in court charged with assaulting Portman on June 8 and two people had been arrested on drug related charges.

Police said the alleged assault wasn't directly related to Portman's disappearance.

Detectives have not been able to find Portman's mobile phone or bank cards and they have not been used since she went missing.

Her passport had not been used either.

The vehicle Portman drove to Auckland, a silver coloured VW Passat, has been recovered and examined.

Anyone with information can call the police investigation team on 0800 723 767 (0800 Rae Portman) or Crimestoppers anonymously on 0800 555 111.

- © Fairfax NZ News