The body of 17-year-old Bronwynne Richardson was recovered from a lagoon off the Murray River on Sunday October 14, 1973, after she was abducted two days earlier on Smollett Street.

She had been physically and sexually assaulted, before her body was dumped in the river.

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Detectives from the homicide squad are now re-investigating her murder under Strike Force Kulaman II.

Homicide Squad Detective Superintendent Scott Cook said detectives will explore every line of inquiry in the hope of finally getting justice for the late 17-year-old.

"Strike Force detectives have been conducting inquiries - both in NSW and interstate - to provide answers to Bronwynne's family," he said.

"We know she was dragged into the station wagon and later driven to a reserve off Howlong Road, about six kilometres west of Albury, where she was physically and sexually assaulted, before being thrown into the Murray River.

"The vehicle itself has not been recovered, but we believe someone would have seen it.

"It's a fairly remote area and we expect the driver had local knowledge.

"There is someone out there who knows who is responsible for her death and we're hoping this reward increase may prompt them to get in touch with police."

The vehicle is described as being similar to a pale green and white 1961 FB Holden station wagon.

Her sister, Fiona Hume, said she hoped investigators get the information they need to deliver justice.

"It's been nearly 46 years since Bronnie died, and our family is still so devastated that we will never see or speak to her again," Ms Hume said.

"Bronnie was a beautiful teenage girl with her whole life ahead of her and it was cut short just before she was about to take part in the Belle of Belles Ball.

"We believe someone in the community knows what happened and has information about those involved in her death.

"Please come forward and speak to the police - now is the time to put things right."

The reward will be offered for information that leads to the conviction of those responsible for Bronwynne's murder.

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