In a tiny desert town, two women vanished just 14 months apart. Police suspect murder.

Roughly 845 kilometres north of Adelaide on the Stuart Highway sits Coober Pedy. A tiny, opal-rich desert town pockmarked by mining shafts and dugout homes that have been built into the sun-scorched earth.

It’s a place just 1700 people call home; countless more come and go, with or without their longed-for fortune. But it’s also a place that’s home to more than its share of mystery.

Between 1990 and 2003, four murders took place in Coober Pedy, all of which remain unsolved. Two decades on, South Australia Police are reviving their investigations into the crimes as part of Operation Persist – an initiative launched in 2015 to review the state’s cold cases.

And now, police are acknowledging possible connections between two.

Karen Williams, 16, and Anna Rosa Liva, 30; two women who disappeared from the town just 14 months apart. Karen, a member of the local Aboriginal community, vanished on August 4, 1990 after a night out with family and friends. Anna Rosa, an Italian tourist, was last seen on November 28, 1991.

Neither woman’s body has ever been found.

Karen Williams’ disappearance.

After a celebration at Sergio’s Restaurant on Coober Pedy’s main street, TAFE student Karen and three friends accepted a lift from a man in the early hours of August 4. While her friends got out of the vehicle near Medway Drive, Karen didn’t.

A short time later, around 5am, the teenager was seen in a vehicle at the local Caltex Service Station.

That was the last known time she was ever seen alive.

Following an extensive inquiry, police charged a man named Nikola Novakovic with Karen’s murder, but in August 2016 he was acquitted by a Supreme Court judge.

A reward of $1,000,000 is available to anyone who provides information leading to the apprehension/conviction of the person or people responsible for her suspected murder and/or leading to the location and recovery of her remains.

Anna Rosa Liva’s disappearance.

An experienced traveller, Anna Rosa arrived in Coober Pedy by bus at 10pm on November 27, 1991. The next morning she booked an afternoon tour of the opal fields and headed off to the council chambers where she inquired about attending a Jehovah’s Witness meeting that night.

She was last seen near the council offices, right in the centre of the bustling township, at around midday. A place, police note, that is in close proximity to where one of the suspects in Karen’s murder lived.

“The location where Anna Rosa Liva disappeared from is certainly interesting,” Detective Sergeant Paul Ward told 9News.

“We keep an open mind on these things. It’s important to consider any possible links.”

No disturbances were reported in the area, leading police to suspect Anna Rosa may have willingly got into someone’s car.

A reward of $200,000 is on offer for information that leads to the recovery her remains and/or the apprehension and/or conviction of the person, or people, responsible for the suspected murder.

Compared to Anna Rosa's case, Karen's received little media attention at the time.

"It's very hard for us," community member Robin Walker told The Age in 1992. "We are part of Coober Pedy but when we saw the helicopters and the dogs we said: `Why didn't they do that for us?'"

South Australia Police are hoping renewed coverage may spark memories or encourage people to come forward, for the sake of both women's loved ones.

"As with all unsolved murders, police are conscious that in each case there is a family who are waiting for answers and are hopeful that one day they will have some explanations about what happened to their loved one," they said in a statement.

"In each of the cases, just one simple piece of information might be all it takes to give police the lead they need."

Police are also appealing for information relating to the murders of Coober Pedy locals Colin Williams in 1995 and Andrew “Wilbur” Williamson in 2003.

Anyone with information about any of these cases – or any unsolved murder or suspicious disappearance – is urged to call Crime Stoppers on 1800 333 000 or report online at www.crimestopperssa.com.au – you can remain anonymous.