The garda helicopter was involved in the search for a 65-year-old Dublin woman with Alzheimer’s, who has been missing since Tuesday morning.

The family of Margaret (Peggy) Mangan have said they are very concerned for her well-being.

She left Mount Tallant Avenue in Terenure for a walk with her dog just after 11am, but has not returned home.

There are reported sightings of the dog on its own today.

Searches are tonight concentrated on the areas of Finglas and Glasnevin.

Family friends and volunteers have joined the search.

Gardaí have appealed for people to search outhouses, particularly in the Phibsboro, Violet Hill, Glasnevin and Dublin industrial estate areas.

Speaking earlier on RTÉ’s Morning Ireland programme, family member Cian Lynch said Ms Mangan was a very active woman and relatives are concerned that she has walked kilometres from her home.

She was seen with her dog, a cavalier King Charles spaniel called Casper, on Clanbrassil Street at around 12pm on Tuesday.

She was spotted on the Finglas Road at about 3pm and again in Phibsboro at 6pm.

The family said the last confirmed sighting of Ms Mangan was near Glasnevin Cemetery at around 6.50pm on Tuesday evening.

Gardaí yesterday released CCTV footage of Ms Mangan walking with her dog.

Ms Mangan is 1.57m (5’2") tall, of very slim build and was wearing black trousers and a white, hooded fleece when she left home.

Her family said she left home with no money and no travel pass. They have appealed to anyone who may have seen her to contact Terenure Garda Station on 01-6666400.