The missing people ACT's government hopes to find with $500,000 rewards - ABC News & Headlines – Australian Broadcasting Corporation

Elizabeth Herfort has not been seen since 1980, when she was 18 years old. (Supplied: ACT Policing)

The ACT government is offering rewards of up to $500,000 for information that leads to the successful prosecution of those responsible for the deaths or disappearances of five individuals.

Anyone with any information about any of these matters is being urged to provide their details to Crime Stoppers.

The government said  "appropriate indemnity from prosecution will be considered for any accomplice to a homicide who first gives information".

Elizabeth Herfort was last seen walking through the centre of Canberra on June 13, 1980.

What happened to her after that remains a mystery, despite repeated attempts to raise awareness over the years.

According to police, Ms Herfort had been out socialising with friends at the Australian National University Bar in Acton.

It is believed she left the venue to catch a bus home, and a person matching her description was seen walking along Vernon Circle and Commonwealth Avenue between 9pm and 9:45pm.

But the 18-year-old never made it home.

The ACT government announced today a reward of up to $500,000 for information that leads to the successful prosecution of the person — or people — responsible for Ms Herfort's disappearance.

"We simply ask that if anyone remembers or knows anything that may be helpful in finding her, or finding out what happened to her, please, contact the police."

Rewards of up to half a million dollars are also being offered by the ACT government for four other unsolved cases — including that of Keren Rowland.

Ms Rowland was 20 years old and pregnant when she went missing on February 26, 1971 — the night of the Royal Canberra Show. 

Her remains were discovered at the Air Disaster Memorial nearly three months later.

Canberra woman Keren Rowland was 20 years old when she died in 1971. (Supplied)

Ms Rowland's brother Steve said a breakthrough would "be like winning the lottery or better", and pleaded that anyone with information came forward.

"We'd just hope it would be helpful for them to get it of their chest, and to pass on whatever they may know," he said.

Steve Rowland said Keren's family was "desperate" for any details regarding her disappearance. (ABC News: Luke Stephenson)

David Abuoi, also known as Gabrielle Malak Arok, was last seen on the morning of July 10, 2012, in Canberra's CBD.

He was 35 years old when he disappeared.

David Abuoi was last seen on London Circuit in Civic in 2012. (Supplied: Australian Federal Police)

Megan Louise Mulquiney, who started work at 8.30am on July 28, 1984, at Big W in the Woden Shopping Centre, also remains missing. 

The 17-year-old was last seen standing outside the western entrance of Woden Plaza about noon that day. 

Megan Louise Mulquiney has been missing since 1984. (Supplied: ACT Policing)

Troy Hugh Forsyth was 17 years old when he was fatally struck by a panel van while walking home with friends along Kent Street in Deakin in the early hours of Sunday March 1, 1987. 

Police never found the panel van nor its driver despite what they called an "exhaustive" investigation, and that case remains open.

Troy Forsyth's mother Valerie Tompkins (left) and his sister Vanessa Forsyth (right) with Sergeant Jason Kennedy in 2012, at the site where Mr Forsyth died. (Kathleen Dyett)

The government said if the disappearance or death of each of these individuals was the result of criminal action, "any witness or person with relevant information may be eligible for a reward".

Police have been unable to locate the driver of the vehicle that struck and killed Troy Forsyth. (Supplied: ACT Policing)

Police, Fire and Emergency Services Minister Marisa Paterson said it was hoped the reward would motivate someone to come forward.

"The families of these five people have never given up hope of getting answers regarding what happened to their loved ones."

ACT Chief Police Officer Scott Lee said these five cases were the most likely to have witnesses or information that could assist police.

ACT Chief Police Officer Scott Lee says there is a chance someone knows something despite the passage of time in each case. (ABC News: Ian Cutmore)

"As we continue to review, reconsider and re-examine each of these matters, we acknowledge that significant time has passed for some of these investigations," he said.

"But that doesn't mean there isn't someone out there that knows what happened.

These five cases are in addition to three existing unsolved homicides that had rewards announced in 2012 — the murders of Kathryn Grosvenor in 2002, Susan Winburn in 2004 and Frank Campbell in 2005.

Anyone with any information about any of these eight matters is being urged to provide their details to Crime Stoppers.

"While information can be provided anonymously, to be eligible for any reward requires the person providing the information to supply their details and speak with police," the government statement said.