She had been in contact with her family almost every day until December 1, the day before her birthday.
Detective Inspector Scott Beard addresses a press conference announcing the search for missing English backpacker Grace Millane is now a homicide investigation in Auckland, New Zealand, Saturday, Dec. 8, 2018.
She arrived in New Zealand last month and was last seen on the night of December 1 entering a central Auckland hotel with a 26-year-old man.
David Millane arrived in New Zealand on Friday morning, after the family raised the alert earlier in the week, having not heard from Grace since Saturday (December 1) - which he said was unusual.
Ms Millane, 22, from Essex, England, was last seen at an Auckland hotel almost a week ago.
Officers and forensic experts are still carrying out a scene examination at the CityLife hotel where Ms Millane was last seen on Saturday 1 December.
He added the "thoughts of all New Zealanders will be with Grace's family tonight".
Grace, from Essex, graduated from the University of Lincoln in September and had embarked on a year-long worldwide trip.
Searches have also been carried out at the backpackers' accommodation where she was staying.
"We still do no know where Grace is".
Investigators had said yesterday that they held "grave fears" for Grace's safety.
A CCTV image shows she was at Sky City, a hotel a short distance away, at 7.15pm on the same night - but her whereabouts between those two sightings is unknown.More news: Ocasio-Cortez Calls on D.C. to Pay Higher Wages for Staffers
Ms Millane (pictured) arrived in New Zealand on November 20.
(AAP) Missing British backpacker Grace Millane has been murdered, police in New Zealand say.
'He was brought back to the Auckland Central Police Station and is now speaking to us in relation to the murder of Grace Millane.
In the statement issued on Saturday, Millane's family praised Auckland police "who have been outstanding in their support and efforts in helping to find Grace".
Asked if they had met on the Tinder dating app, the detective said: "I'm not going to speculate on how they met".
Det Insp Beard confirmed today that the man being questioned by police on Saturday was the same individual.
Police want the public to help find this necklace belonging to backpacker Grace Millane.
A tearful David Millane appealed to the public to come forward with any information, "no matter how small".
He tearfully explained that his daughter has never been out of contact with her family for such a long period of time, usually contacting them on social media.
This was her first time travelling overseas alone.
Grace's father today said: "Grace is a lovely, outgoing, fun-loving, family-orientated daughter".
Detective Inspector Scott Beard said he told Millane's devastated father, David Millane, on Saturday that they believe Millane was killed.
Anyone with information about the missing items has been advised to contact 0800 676 255.