Police will charge a 26-year-old man with the murder of missing backpacker Grace Millane. "We are determined to find her and return her to her family".
Detective Inspector Scott Beard said evidence they had found led them to believe Grace was "no longer alive".
A 26-year-old man - who was with Miss Millane before she went missing - is being held in Auckland in connection with the murder.
"Grace's family have been advised of this development and they are devastated".
CCTV cameras captured Millane at the CityLife Hotel on Queen St at 9.41pm on December 1.
He added the "thoughts of all New Zealanders will be with Grace's family tonight".
Ms Millane was in New Zealand on a gap year, having arrived in the country on November 20.
Searches have also been carried out at the backpackers' accommodation where she was staying.
When asked if Millane knew the man before the evening she disappeared, Beard would only say that "we don't have any evidence of that at this stage", and wouldn't comment on whether the pair met on Tinder.
He wouldn't speculate where Grace was killed, Beard said.
"All I can say is that we know they were together from the time at the Sky City Hotel".
Her birthday was on Sunday but she didn't contact her family.
Millane had been in New Zealand for two weeks, the UK's Press Association news agency reported.
Her father David Millane fronted a press conference at Auckland Central Police Station on Friday after flying to New Zealand from Essex.
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".
Police said they had received dozens of calls to a hotline and more than 25 staff were working on the case, trawling through hours of CCTV footage to trace her movements.
DI Beard confirmed that the man being questioned by police on Saturday was the same individual. Beard said they're also examining a vehicle and want to figure out where it has been driven over the past week.
Her father, a 60-year-old property developer, fought back tears as he urged anyone who has any information about his "outgoing, fun-loving" daughter to come forward.
This was her first time travelling overseas alone.
"Her family are devastated", he said.
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.
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