A woman who was told her mum had walked out on her family when she was 18-months-old has finally learned the truth, as police excavate remains found in the family yard and her dad is in custody.

Kaye Adams, the youngest daughter of Colleen Adams, who had been missing from the Yorke Peninsula in South Australia for 45 years, said in a note read by police: "At last I have found my mother."

"After 45 years of hoping, we have found her," she wrote.

The note from Colleen Adam's daughter which was read by police. (9News)

The daughter of Colleen Adams, who does not want to be identified, arrives at the dig site today. (aap)

Excavation work has begun for the body of Colleen Adams with police 'confident' she will be recovered today. (AAP)

"It's hard to say in a few words what I am feeling.

"I am thankful that the truth has come out and I put my trust in the legal system now."

Police believe the remains belong to missing mum Colleen , after her husband Geoffrey Adams, 70, appeared to point to the concreted area of his yard in dramatic scenes captured by Nine News cameras yesterday.

Forensic officers and anthropologists are on the scene. (AAP)

Friend Claudine Lehner said today: "I just couldn't believe it. He knew she was there."

As the dig in Maitland was taking place, Colleens husband, Geoffrey Adams, 70, was facing court in Kadina charged with her murder .

He did not apply for bail and the case has been adjourned to October 5.

Colleen Adams disappeared in 1973 and has not been seen since. (9NEWS)

Ms Adams was a mother of two, and was reported missing by her mother a month after she disappeared. (Supplied)

Police and forensic experts will now focus on recovering Mrs Adams' remains from that site, a metre below the ground.

Mr Adams had previously told police he awoke about 7am on November 22, 1973, to find Mrs Adams fully dressed with two packed suitcases.

Adams pointed out the area he said Colleen's body may be buried. (9news)

Geoffrey Adams meets police at his former Maitland property. (9news)

Police are excavating the site. (9news)

According to Mr Adams, she said she was leaving and never wanted to see him or the children again, before getting into a car with a middle-aged woman he did not know.

Yesterday police revealed they had this week returned to the property to dig for clues in the cold case.

As the operation unfolded, Mr Adams spoke exclusively to Nine News, protesting his innocence.

Geoffrey Adams was arrested by SA police and is assisting with their investigation. (9NEWS)

Police officers dig up part of the backyard in Maitland, South Australia, where Colleen Adams used to live. (SA Police)

He said he believed the mother of two was still alive.

"I just hope that she's well and enjoying life yeah," Mr Adams said yesterday.

Mrs Adams was reported missing by her mother about a month later, but the case was not declared a major crime until 1979.

SA Police Head of Major Crime Des Bray said Mrs Adams' family have been contacted about the developments in the case.

"It is important that we provide answers to family members in cases such as these," he said.

A candle was lit by a police officer who guarded the excavation site last night.