The family of a missing elderly woman suffering from Alzheimer's warned the Bribie Island retirement village from where she disappeared of her tendency to wander off.

But Marian Wallace's family believes the 71-year-old may have been missing for two hours before staff realised she was gone.

The search continues for Mrs Wallace, who was last seen about 3pm leaving the Embracia Retirement Village in Bongaree.

Police officers, water police, sniffer dogs, SES crews and volunteers have spent the last two days looking for Mrs Wallace.

The Brisbane-based helicopter Polair2 has also been called in to search thick bushland using heat-seeking technology.

Her daughter Sue Harrison said Mrs Wallace only moved into the retirement village's dementia ward on Thursday.

Ms Harrison said Mrs Wallace was living independently on the island with her two dogs previously. However the family made the decision to move her to Embracia when her Alzheimer's worsened.

"In the last month she'd started locking herself out of the house or locking herself in. She started walking the dogs at night and doing unsafe things like that," Ms Harrison said.

"When I [took] her to Embracia on Thursday afternoon I explained that she is not safe to be by herself ... if you don't watch her like a hawk, she'll get out."

Ms Harrison said Mrs Wallace had difficulty walking because of an injured hip, but added that she was "pretty tough" and "very fit".

"A lot of people - when you first meet her - may not be aware that she has Alzheimer's. It's only when you ask her more things you realise something isn't right," she said.

Mrs Wallace was last seen leaving the Bongaree facility on Goodwin Drive, walking up Sunderland Drive towards the Banksia Beach and Pacific Harbour area.

The 71-year-old is described as being 165 centimetres tall, with a small build and grey hair. She was wearing a green cardigan, light blue jeans, black shoes and was possibly carrying a hand bag.

Police do not believe Mrs Wallace took a bus or taxi off the island, but cannot rule out the possibility that she may have left. They believe she would have been in "a confused state".

Police have asked drivers with in-car cameras, who were heading along Sunderland Drive between 3-5pm on Sunday, to check whether Ms Wallace was captured in any footage.

"Given the inclement weather over the past couple of days, Marian's age and her mental condition we do have real fears and concerns for her safety. But we're very hopeful by the same token," Bribie Island Sergeant Jimmie Driver said.

Embracia chief executive Wally Bourdelov said it was "very rare" for residents to disappear from the retirement village.

He said it was inappropriate to comment on the circumstances of Mrs Wallace's disappearance while the police search was under way.

"We do take the welfare and safety of our citizens seriously. The moment we found the resident missing we notified the family," Mr Bourdelov said.

"Places like ours are a resident's home, it's not a prison. It is their home and we try and make it as homely and caring for them."

Anyone with information should contact Bribie Island Police on 3410 9222 or Crime Stoppers on 1800 333 000.

Final searches of Bribie Island for missing elderly woman

Police divers are today searching the canals and estuaries on Bribie Island in the hope of finding clues to the disappearance of Marian Wallace.

The 71-year-old has been missing since Sunday and so far there are no clues as to where she may be.

SES crews and police are today scouring bushland on quad bikes and on foot.

The whole of the Island will have been searched by the end of the day.

Sergeant Ryan Hanlon says authorities at this stage believe Ms Wallace just "wandered off" however an extensive police investigation is underway in conjunction with search efforts.