A 30-year-old woman has been arrested for allegedly assaulting missing woman Rae Portman in the days leading up to her mysterious disappearance.

Ms Portman, 33, a known drug user, has not been seen since June 20 and her phone and bank accounts haven't been touched.

Police hold grave fears for her safety.

Detective Inspector Mark Gutry said officers investigating the disappearance had arrested a 30-year-old Manurewa woman.


It was alleged the woman assaulted Ms Portman at a Manurewa property on June 8.

The arrest was not related to Ms Portman's disappearance, Mr Gutry said.

"The investigation team have been investigating Rae's movements in the days leading up to her disappearance."

The woman is due to appear at Manukau District Court on August 20.

Ms Portman, who is unemployed and goes by the nickname Bok, had driven from Hamilton to Auckland on June 20 and visited friends in Glen Innes in East Auckland and in Papakura, South Auckland, before she went to the Mt Albert Motor Inn.

Most of her belongings were found at the motel.

However, her cellphone and other belongings, such as her purse, were not found.