The parents of Nóra Quoirin, who have strong links to Derry, have said they believe there was a "criminal element" to their daughter's disappearance and death in Malaysia in August.
The 15-year-old disappeared while on a holiday with her family at a resort in a nature reserve near Seremban, 63 km south of Kuala Lumper, Malaysia, on August 4. Her body was discovered ten days later.
In an interview with RTÉ, Nóra's parents Meabh and Sebastian Quoirin said they believed there were questions about how their daughter got to the stream where she was discovered about 2 kilometres from the Dusun rainforest resort where they were staying.
Meabh, from Belfast, and Sebastian, from France, met while at Magee College in Derry in the 1990s.
"For us something very complex happened. We have insisted from the beginning that we believe there was a criminal element to what happened.
"And crucially we're struggling because it was difficult to get resources in place fast enough to investigate a criminal angle," said her heartbroken mother Meabh.
Meabh and Sebastian said they did not believe Nóra, who had special needs, would have wandered so far from her family.
While a post-mortem examination in Malaysia found that Nóra died from intestinal bleeding, probably caused by hunger and stress, Meabh and Sebastian are still waiting for full post-mortem results from the south-east Asian country.
They also await the results of a separate autopsy that was carried out in London following the repatriation of Nóra's remains.
"While a post-mortem when it comes through may give us answers, and has already given us some basic answers around what caused Nóra's death, it doesn't explain any of how she could possibly have got to where she was found," said Meabh.