South Australia Police plan to dig up a factory site near Glenelg Beach, where three children from Beaumont were last seen more than 50 years ago.

Police will in the coming fortnight excavate part of a factory site in North Plympton, a suburb of Adelaide, following geophysical investigations and new information from witnesses. The factory was previously owned by a now deceased man who was investigated but not named as a suspect.

Jane Beaumont, 9, her sister, Arnna, 7, and brother Grant, 4, have been missing since 26 January, 1966. They were last seen on Glenelg Beach, around three miles (5 km) from the factory site.

The South Australian government and police have offered a $800,000 ($1 million Australian dollars, reward for information regarding the case, ABC reported. Credit: South Australia Police via Storyful