SEREMBAN, Malaysia (AP) — Malaysian doctors conducted a lengthy autopsy Wednesday to determine the cause of death of a 15-year-old London teen whose naked body was found nine days after she mysteriously disappeared from a nature resort.

Nora Anne Quoirin's body was discovered Tuesday beside a small stream about 2.5 kilometers (1.6 miles) from the Dusun eco-resort in southern Negeri Sembilan state, where she went missing on Aug. 4. The body was airlifted to a hospital, where she was identified by her parents.

Negeri Sembilan deputy police chief Che Zakaria Othman told reporters at the hospital morgue that the post-mortem was still continuing late Wednesday, more than eight hours after it began. He said it was conducted by a medical team including a senior pathologist from Kuala Lumpur, and that he couldn't say how long it would take.

Police hope to release details of the autopsy on Thursday, he added.

Local media reported that a forensic team also went back to the area where the body was found to search for evidence. Police didn't say how long the body had been there or why rescuers apparently missed it earlier in the search operation.

Her family earlier Wednesday thanked the more than 350 people who helped search for the girl, who has learning and physical disabilities.

"Nóra 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," the family said in a brief statement issued by the Lucie Blackman Trust, a charity that helps families of Britons in crisis overseas.

"We will always love our Nóra," they said.

Police from Ireland, France and the U.K. are in Malaysia to assist in the investigation. The girl's mother is from Ireland and her father is French, but the family has lived in London for 20 years.

Malaysia's queen joined Cabinet ministers and foreign leaders in sending condolences to the Quoirin family.

"May God give you the strength in your hour of need," Queen Tunku Azizah Aminah Maimunah Iskandariah tweeted.

French Foreign Affairs Minister Jean-Yves Le Drian and Secretary of State Jean-Baptiste Lemoyne said they were grateful for the solidarity shown by the Malaysian people. "French authorities are at the disposal of Malaysian authorities so that full light is shed on the circumstances of her death," they said in a statement.

Irish Prime Minister Leo Varadkar said the family has "experienced every family's worst nightmare."

"I'd like to pay tribute to everyone who searched for Nora. May she rest in peace," he tweeted.

The Paris prosecutor's office said Wednesday that it has opened a preliminary investigation into the girl's death, on potential charges of kidnapping and sequestration. The prosecutor's office wouldn't elaborate. French authorities often open such investigations when French citizens are victims or otherwise involved in suspected crimes abroad.

Quoirin's family arrived Aug. 3 for a two-week stay at the Dusun, a small resort located in a durian orchard next to a forest reserve 63 kilometers (39 miles) south of Kuala Lumpur.

Police believe the teen climbed out through a window in the living room of the family's resort cottage. They listed her as a missing person but said the investigation included possible criminal aspects. The girl's family has said she isn't independent and wouldn't wander off alone, and was likely to have been abducted.

Sankara Nair, a Malaysian lawyer hired by the family, said Wednesday that the family hopes police will investigate possible foul play in her death. If the autopsy isn't conclusive, he said the government could hold an inquest later on to identify the cause of death.

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