(CNN)The family of missing teenager Nora Quoirin, who vanished from a remote resort in Malaysia on Sunday, say they believe the 15-year-old Londoner was abducted.
Quoirin's parents say they found her bedroom empty and a window open on Sunday morning.
The teenager has a learning disability and her parents said they have "no reason to believe she wandered off and is lost."
Malaysian police, who are leading a large search operation in the surrounding jungle, have not ruled out an abduction. But they have said there are no initial signs of foul play, according to the UK Press Association (PA).
Quoirin's family, however, insisted that she would not have left her bedroom herself.
"Nora's family believe she has been abducted," they said in a statement carried by PA. "We are especially worried because Nora has learning and developmental disabilities, and is not like other 15-year-olds."
"She looks younger, she is not capable of taking care of herself, and she won't understand what is going on," they added. "She never goes anywhere by herself. We have no reason to believe she wandered off and is lost."
The Dusun resort, where the family were staying, is in a remote area 800 feet above sea level in the Titiwangsa mountain range. It contains six houses, each surrounded by rainforest, and has capacity for just 20 guests.
In a statement posted online, the management of the Dusun resort said that hotel staff searched the 12 acre (48,562 square meter) property "all Sunday morning," before then joining the wider police search. That search has now expanded, according to local media.
Quoirin, who has an Irish mother and a French father, was traveling on an Irish passport during the trip.
She is five foot and one inch tall (155cm), has a slight build, wavy shoulder-length dark blonde hair and blue eyes, according to the Lucie Blackman Trust (LBT), a charity which has been assisting the girl's family.
Aisling Agnew, Quoirin's aunt, was quoted by LBT as saying: "Nora's parents and relatives in Ireland and France are distraught by her disappearance. Nora is a child with special needs and has learning and developmental disabilities which make her especially vulnerable and we fear for her safety."
"Nora would not know how to get help and would never leave her family voluntarily. We now consider this a criminal matter. We are appealing to everyone to assist the local police in any way they can and to pass on any information that would help locate our beloved Nora without delay."