New lead in SA's Beaumont cold case

South Australia's most enduring cold case is to be revisited, with the site of an Adelaide factory to be dug up again following new information on the missing Beaumont children.

Investigations into the 1966 disappearance of nine-year-old Jane, Arnna, seven, and four-year-old Grant have led detectives back to the factory they first excavated in 2013.

A fresh dig at the North Plympton site, which is now the Castalloy factory, will begin in the next few weeks, police say.

The Seven Network conducted their own investigations into the site and passed information to South Australian police.

"Channel 7 has made available to SAPOL results of geophysical investigations which in conjunction with fresh information from witnesses has led police to examine a new area at the rear of a factory, which is now Castalloy," the police said in a statement on Monday.

The Beaumont children failed to return from a trip to Glenelg Beach on Australia Day more than 50 years ago.

The state government has offered a $1 million reward for information leading to an arrest and conviction or the discovery of the victims' remains.

A book in 2013 raised a theory that the children were buried at the North Plympton factory, but nothing was found in a later police excavation.