(CNN)Police in New Zealand are searching for a British backpacker who has been missing since December 1.
Grace Millane, 22, was last seen in the center of the city of Auckland, a major city on New Zealand's North Island, around 7 pm on Saturday.
Detective Inspector Scott Beard of Auckland City Police said Millane had not made any contact with her family for days.
"This is particularly out of character, especially as it was her 22nd birthday on Sunday," said Detective Inspector Beard in a statement.
"We are working closely with her family at this time and a number of Police staff are currently working on this matter."
Police have released a CCTV image of Millane at Sky City, an entertainment complex.
She had been in New Zealand for two weeks and was staying at a hostel in Auckland, the UK's Press Association news agency reported.
Members of Millane's family have made Facebook posts appealing for information.
Members of the public have reported several sightings but they remain unconfirmed, according to police.
"Clearly this is a very stressful time for Grace's family and the longer she remains missing the more our concern grows for her safety and wellbeing," added Beard.
"We are providing consular support to the family in the UK, and working with the New Zealand Police in relation to reports of a missing British national in New Zealand," a spokesperson for the UK Foreign Office said in a statement.