Police have excavated a factory site in Adelaide over the disappearance of three children more than 50 years ago.

The case of the Beaumont children is often described as Australia's most enduring cold case mystery.

The children - Jane, nine, Arnna, seven, and Grant, four - vanished after visiting a beach in Adelaide in 1966.

The new search, at a site once owned by a person of interest in the case, followed a recently discovered "anomaly" in the soil.

The factory site, in the suburb of North Plympton, is about 5km (3 miles) from Glenelg Beach, where the children were last seen after going for a swim.

The dig took place on Friday, but was called off after nothing of interest was found.

Detective Chief Superintendent Des Bray told reporters several animal bones had been found but "nothing human".

"Sadly this means for the Beaumont family we still have no answers, we still have a lot of work to do," ABC quoted him as saying.

The property once belonged to a local businessman, Harry Phipps, who died in 2004. He remains a person of interest in the case.

A separate area of the site was excavated in 2013, but no evidence was discovered.

Police said their investigation would attempt not to cause unnecessary distress to the children's elderly parents, Jim and Nancy Beaumont.

"We all must remember the two Beaumont family parents who [have] suffered significantly over many, many years," Detective Chief Inspector Greg Hutchins said earlier on Friday.

The South Australian government has offered a A$1m (£560,000; $800,000) reward for information that helps solve the case.