The family of missing Tyrone teenager Arlene Arkinson have queried whether Gardai are sharing all "possible leads" with PSNI, after it emerged a body suspected to be hers was first known to officers in 1999.
The 15-year-old, from Castlederg, who disappeared in 1994 after a night out in Bundoran, Co Donegal, was last seen in the company of convicted child killer Robert Howard.
Howard, who died in 2015, was acquitted of Arlene's murder in 2005, but is still regarded as the prime suspect.
The schoolgirl's remains have never been found, but her family's hopes were raised after remains found in Co Sligo were exhumed.
Her sister Kathleen Arkinson said they have been informed that the body is not hers.
"My hope in finding the remains of my sister, Arlene, have been dashed again," she told the BBC.
"I prayed it was Arlene and was devastated when I was told it wasn't.
"We seem to suffer blow after blow. "
The body, which was exhumed in March, is alleged to be that of a woman with long hair, wrapped in plastic.
It is reported that Garda files showed that the remains were discovered in 1996 by gravediggers two to three feet beneath the surface as they prepared for a burial.
However, it is alleged it was not reported until three years later, when a local priest was told about the discovery.
One of the explanations why it was not reported in 1996 was concern that the IRA had something to do with the death.
At that time a decision was taken not to exhume the body.
However, details about the body emerged when the files obtained by the coroner in Belfast as part of an ongoing inquest into Arlene's death.
"Did the Garda ever tell the RUC about this body, that's what I want to know" Ms Arkinson told the BBC.
"This was an obvious lead for those searching for Arlene and it's only coming out now. It makes me wonder how many other possible leads the Garda had and didn't share them."
The inquest into the teenager's death is due to resume on Monday.