Rewards of $1 million are on offer for information to help solve some of South Australia’s high-profile missing children cases.

Kirste Gordon was four and Joanne Ratcliffe 11 when they were abducted from Adelaide Oval in 1973.

Four decades later, police still do not know what happened to the girls and the passage of time has failed to ease the loss for relatives.

But Joanne Rattcliffe’s sister Suzie hopes the reward now on offer can lead to new information.

“Living day by day not knowing where our children are … it’s incomprehensible. It’s a pain that no one should have to endure,” she said.

There are 13 cases involving 18 missing children, including the Beaumonts, with $1 million reward for details resulting in a conviction.

Police say any tip-off leading to remains also will attract the payment.

Assistant Commissioner Paul Dickson thinks $1 million is a strong inducement for someone to come forward.

“They may have concerns about their own personal safety or their relationships with others so we need to actually assist them to be able to come forward and that’s what part of the $1 million reward is about,” he said.

The South Australian Government acted on recommendations from police to boost the reward money.

Police say the big rewards are motivated by arrests in cases such as over the disappearance of Louise Bell in at Hackham 1983 and teenager Karen Williams at outback Coober Pedy in 1991.