Rosemary Brown, 33, and her daughter Melisssa Trussell, 15, were last seen in Blair Athol, around 4km from Adelaide’s CBD, at around 2.30am on May 13, 2000.

Rosemary’s handbag was found later that same day on Stirling Street in Northfield.

It was not handed into police until May 23 following a public appeal about the missing women.

Nearly two months later on July 2, Rosemary’s body was discovered in mangroves at Garden Island, a city north-west of Adelaide.

Melissa has never been found and police believe she was murdered.

On the 25th anniversary of the discovery of Rosemary’s remains, police have asked the public for assistance in solving the “disturbing” double cold case.

Detective Superintendent Darren Fielke said police were using the grim milestone to hopefully encourage somebody with information to come forward.

“As you can imagine, that’s 25 years of ongoing pain and suffering for the family not knowing what has happened to Rosemary and Melissa,” Fielke said.

“This case is particularly disturbing in that we found the body of a murdered mother, and we have a 15-year-old girl who remains missing and we suspect has been murdered.”

Fielke shared never-before-seen photographs of the mother and daughter.

He said their loved ones, particularly Rosemary’s father and sister, are still overcome with grief.

Fielke said police are following “positive lines of inquiry” into Rosemary’s murder and Melissa’s disappearance and was hopeful the investigation was close to a breakthrough.

“But we can always have more information and sometimes it’s those little pieces of the jigsaw we are looking for to put it all together,” he added.

A $1 million reward remains on offer for anyone with information which leads to the conviction of those responsible.