Teenage holidaymaker Nora Quoirin died from intestinal damage most likely caused by starvation and stress, according to Malyasian police.
Police say there is no evidence the 15-year-old was kidnapped or raped, after post mortem results were released on Thursday.
When Nora was still missing her family said they believed she was abducted, but police insisted she had likely climbed out of a window, wandered off from a holiday cottage and got lost in the dense jungle.
The Franco-Irish teen, who has special needs, was found dead on Tuesday, more than a week after she disappeared during a two-week family holiday at a resort south of Kuala Lumpur - reports Mirror Online.
The results of a post-mortem , conducted at a hospital in the nearby town of Seremban, were announced on Thursday, and they were in line with the police theory.
Nora, who was born with the brain defect holoprosencephaly and was described by her family as "vulnerable", disappeared on August 4, a day after her family checked into the Dusun resort.
Her unclothed body was discovered on Tuesday beside a small stream about 1.6 miles from the cottage where she was staying with her parents, Meabh and Sebastien, and her younger brother and sister.
Police said the body was found in an area that had previously been searched by rescuers.
In their most recent statement, Nora's devastated family said their "hearts are broken" and paid tribute to her as "the truest, most precious girl".
They made an emotional statement released through the Lucie Blackman Trust , describing how the teenager, who lived in London, had "truly touched the world".
They said: "Nora is at the heart of our family. She is the truest, most precious girl and we love her infinitely.
"The cruelty of her being taken away is unbearable. Our hearts are broken."
They offered thanks to those involved in the search for the teenager, adding: "Nora has brought people together, especially from France, Ireland, Britain and Malaysia, united in their love and support for her and her family."
Hundreds of people were involved in the search operation and it was volunteer helpers who found the teenager's body.
Search and rescue teams had used helicopters and drones with thermal imaging cameras, sniffer dogs, local shamans who summoned spirits during rituals and indigenous villagers during the effort involving more than 350 personnel.
