Detectives have made a breakthrough in the investigation into the abduction and suspected murder of a three-year-old girl from a beach on the New South Wales south coast more than 40 years ago.

Toddler Cheryl Grimmer vanished from Fairy Meadow beach, near Wollongong, in January 1970, where she had been with her mother and three brothers.

Detectives and her brothers Ricky, Paul and Stephen Grimmer are expected to reveal they suspect she was taken by a teenager who would now be in his early 60s.

An inquest into the death four years ago found the toddler probably died on the night she was abducted, but her survival could not be ruled out.

Local surf club member Steve said he was one of hundreds of people who scoured sand hills for the three-year-old in 1970.

“It was a beautiful summer’s day and the beach was busy and then all of a sudden there was this outcry — ‘where’s Cheryl?’.”

“So the next few days I think it was we just searched and searched, but no trace of course.

“We turned every stick over.”