Investigation into missing SA baby renewed

An investigation into the disappearance of a baby boy taken from his grandparents' Adelaide home more than 40 years ago has been renewed.

Darren Jason Shannon, 11 months old, was taken by his father Jason in June, 1973, hours before the 25-year-old died in a car crash north of the city.

Baby Jason, as he was dubbed, was not found in the wreckage.

While police suspect murder, they are still holding out hope that he was left with friends.

"He would be 44 now and his mother, Michelle, who has remarried and now lives in the UK, has never stopped wondering what happened to her son," authorities said on Sunday, during National Missing Persons Week.

"If a friend of the family knows of a 'secret' baby, or helped raise this child, we would appeal for them to come forward to lay this mystery to rest."

Over the past 18 months, authorities have revisited forensic material and detailed case reviews, and have sought DNA and fingerprints from those convicted of murder or manslaughter.

Anyone with information that could help investigators has been asked to call Crime Stoppers on 1800 333 000.