A woman who never returned home from her walk on Auckland's North Shore has not used her mobile phone or accessed her bank account since Monday.
Police are baffled by the unexplained disappearance of 44-year-old Asian woman Bin Chen, who was reported missing by her distressed partner after she failed to return from her regular evening walk.
Ms Chen, who is known as Cissy, left her Torbay home about 5.30pm on Monday.
Large aerial, ground and shoreline searches have failed to find her and today police will investigate new areas to search, Acting Detective Senior Sergeant Megan Goldie said.
Ms Chen regularly went on hour-long walks in an area of Long Bay Regional Park, which was close to her home.
Ms Goldie said about 30 staff were involved in searching for Ms Chen and today they would look further north than where Ms Chen normally walked.
"I wouldn't say it's dense bushland ... but there are some steep areas, areas where if she has accidentally fallen into it would be hard for her to be located," Ms Goldie said.
"We are keeping an open mind as to where she went on Monday evening but ... our concern for her welfare and well-being is certainly mounting."
Police have appealed for information from any residents in the Long Bay, Waiake and Torbay areas who were out walking between 5.30pm and 10pm on Monday.
"Any recent sightings of Cissy will significantly help our existing enquiries," Ms Goldie said.
"A police search and rescue team is canvassing an area north of Long Bay.
"The police helicopter Eagle made several sweeps over the Long Bay Regional Park location yesterday and [police launch] Deodar also carried out a search along the coastline.
"Further sweeps are being planned."
Anyone with information should call North Shore police on 09 477 5207 or Crime Stoppers no 0800 555 111.