Police say they will charge a 26-year-old man with the murder of Grace Millane.

Earlier on Saturday Detective Inspector Scott Beard said Police had launched a homicide investigation into her disappearance and a man had taken in for questioning.

"The 26-year-old who has been speaking with Police in relation to the disappearance of Grace Millane will be charged with her murder," a police spokesperson said on Saturday night.

"He will remain in Police custody until Monday morning when he will appear in the Auckland District Court."

Ms Millane was last seen with the suspect last Saturday evening at the CityLife Hotel. It is unknown if she left there alive.