It has now been five days since Auckland woman Patricia Wearn was last seen.
Police Search and Rescue and LandSar volunteers are today searching dense bush near Torbay, including Glamorgan School.
Last night about 9.40pm a report was received of a woman of a similar description to Wearn in the Torbay area.
However, after a large number of search and rescue staff went to the area nothing was found.
The 73-year-old has not been seen since she left her Caversham Drive home in Torbay to go for her regular walk at 12.30pm on Monday.
Police have been going door-to-door, talking with residents, and asking them to search their properties, sheds, garages and small spaces such as dog kennels.
Police are consulting search and rescue medic Dr Sara Gordon to determine Wearn's survivability expectations.
"Pat is likely to be very dehydrated and therefore more confused and disoriented than usual. She may be critically unwell and we are extremely concerned for her well being," Gordon said.
Police said Wearn may be in a place she is unable to escape from, such as a property with a gate, under a shelter or in the bush.
"We urge everyone to check their properties in any area that someone would be able to seek shelter, including bush areas. Anyone who can't do this properly by themselves should contact police and we can look to provide assistance," Gordon said.
North Shore Police Inspector Sunny Patel said the search continued in the hope Wearn is alive.
"Our search is concentrated in the Torbay area because this is the last confirmed sighting of her."
Officers are also continuing to review hours of CCTV footage taken from the Torbay, Browns Bay, Northcross, Windsor Park and Pinehill areas.
Traffic camera footage from main intersections is also being reviewed.
Anyone with information is asked to contact police immediately.