A postmortem of Nora Quoirin, the 15-year-old girl who went missing in the Malaysian jungle, has yet to determine a definitive cause of death and will continue on Thursday, say police.

The body of the teenager, from London, was discovered by a team of local hikers on Tuesday afternoon. She had been missing for 10 days.

Nora’s body was found unclothed down a steep, inaccessible ravine near a stream, just over a mile from the resort where she had been staying with her family, and was winched by helicopter to a hospital, according to an official.

Police said the area had already been searched by rescue teams days earlier.

Nora’s Irish and French mother and father, Meabh and Sebastien Quoirin, identified her body on Tuesday night. The autopsy was carried out on Wednesday by a pathologist from Kuala Lumpur general hospital, a local hospital doctor and two experts from the department of chemistry.

Speaking outside the morgue at Tuanku Ja’afar hospital, the Negeri Sembilan deputy police chief, Che Zakaria Othman, said on Wednesday: “Today the postmortem started at 11:45am. The four-man team are still carrying out their work so the police cannot tell the criminal investigation division (CID) the results yet. There is nothing more we can say for the moment.”

It is understood the Malaysian attorney general, Tommy Thomas, has stepped in to oversee the case and has requested test samples from the postmortem.

Nora was born with holoprosencephaly, a neurological disorder, which limited her speech and coordination and made her “very vulnerable”, according to her parents. During the search, her family said she must have been abducted as she “never goes anywhere by herself”, but police have so far treated the case as a missing person, while not ruling out a “criminal element” in the teenager’s disappearance.

Facebook Twitter Pinterest Nora Quoirin’s mother, Meabh Quoirin, with the police chief, Che Zakaria Othman. Photograph: Sanghwan Jung/Rex/Shutterstock

In a statement on Wednesday, the family described their agony at Nora’s death in a statement, describing her as “at the heart of our family”.

“She is the truest, most precious girl and we love her infinitely,” said the family. “The cruelty of her being taken away is unbearable. Our hearts are broken. We will always love our Nora.”

They thanked all those who had been involved in the search to find her, adding: “Nora has brought people together, especially from France, Ireland, Britain and Malaysia, united in their love and support for her and her family. She has truly touched the whole world. To all our friends and family at home, we can’t thank you enough for all your love.”

The Lucie Blackman Trust, which has speaking on behalf of the family, called for “an end to speculation, please let the family grieve in peace and the authorities do their job”.

The Paris prosecutor’s office said it had opened a criminal investigation into Nora’s death. French prosecutors regularly investigate cases involving French citizens abroad.

The discovery of the body drew to a close a 10-day search operation that involved more than 350 people, including British, French and Irish police officers. Nora disappeared on 4 August from the hotel room she was sharing with her brother and sister at the Dusan resort in the Negeri Sembilan area of Malaysia, where the family had arrived for a two-week holiday. A window was found open downstairs.

Sankaran Nair, the lawyer representing the family, said: “They are totally distraught and totally overwhelmed. Right now they are grieving.”

The resort borders thick jungle and helicopters were still circling the area the morning after Nora’s body was found.

On Monday, Nora’s mother had made an emotional appeal for help in finding her daughter and a £10,000 reward was offered by an anonymous Belfast-based business for information leading to her safe return.