Nancy Beaumont, the mother of the three missing Beaumont children, has died in Adelaide aged 92.

Mrs Beaumont died on Monday in a nursing home. Her death was confirmed in a notice published on Thursday.

The disappearance of her three children – Jane, 9, Arnna, 7, and Grant, 4 – on Australia Day in 1966 is one of the country’s most enduring mysteries.

The children never returned after leaving their parents’ home for an afternoon at Glenelg Beach. There was an intense search but they were never found.

Nancy and Jim Beaumont, the parents of the missing children.

In 2013, investigators scoured a factory west of Adelaide, after two brothers told police they had spent the 1966 Australia Day weekend digging a large hole on the site at the request of the owner Harry Phipps.

Mr Phipps died in 2014 but his son, who accused his father of sexual abuse, believed he was linked to the missing children.

The factory site was excavated in early 2018 but no trace of the children was found.

The children’s father, Jim Beaumont, is also aged in his 90s, and is living in Adelaide.

A funeral notice published in The Advertiser said Mrs Beaumont would be cremated in a private ceremony.