Nora’s body was found near a jungle stream 10 days after she went missing from the resort where she was staying with family.
The teenager found dead in Malaysian jungle after vanishing on a family holiday had not been abducted, police say.
A Post-mortem revealed that Nora died from internal bleeding thought to be caused by prolonged hunger and stress.
Investigators said she had been dead for up to three days when the body was found.
She was described by her family as vulnerable having been born with holoprosencephaly, a disorder which affects brain development.
Negeri Sembilan state police chief Mohamad Mat Yusop, said: “For the time being, there is no element of abduction or kidnapping.
“The cause of death was upper gastrointestinal bleeding due to duodenal ulcer, complicated with perforation.”
Further analysis would be carried out on samples taken from her body, he said, adding Nora’s family was now free to take her home.
Speaking after her body was found, Mr and Mrs Quoirin said their “hearts are broken” and paid tribute to their daughter as “the truest, most precious girl”.
They said Nora, who lived in London, had “truly touched the world” after her disappearance sparked a huge search operation and good wishes from across the globe.
A Belfast book of condolence has opened in a “clear and positive” show of solidarity with Nora Quoirin’s family. Sinn Fein Lord Mayor John Finucane was the first to sign it at the City Hall. Nora’s mother Meabh is from Belfast.
In a statement, the Dusun resort said it wanted to “extend support and assistance in whatever way possible to the Quoirins during these very difficult times”.
“We deeply regret that this has happened to the Quoirins during their stay here,” it said.