A Cambridge student who plunged from a plane in Madagascar was "mumbling" and "incoherent" in a phone call two days before her death, her uncle says.
Alana Cutland's family believe she was hallucinating on prescription drugs and didn't intend to kill herself when she opened the plane's door and jumped out, it was reported.
The 19-year-old's body has not been found after she plunged up to 3,700ft into the savanna on the Indian Ocean island, where she was researching the endangered blue crab.
Ms Cutland's uncle said she had became sick during her time in Madagascar, possibly due to prescription medication, although reports have claimed police are investigating her possible use of an anti-malaria drug.
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"She had taken ill after being there for a few days and when she spoke to her mother on the phone two days before the accident she was mumbling and sounded pretty incoherent," Lester Riley, the brother of Ms Cutland's mother Alison, told MailOnline.
"We think she had suffered a severe reaction to some drugs but not anti-malaria ones because she had taken those on her trip last year to China without any side effects."
It was reported Ms Cutland suffered "paranoia attacks" during her trip.
The Biological Natural Sciences student, from Milton Keynes, Buckinghamshire, was due to spend six weeks in Madagascar, where she was carrying out research in the remote area of Anjajavy.
She was on her way back to the UK on July 25 after she had reluctantly agreed to cut short the trip at her parents' request, it was reported.
Mr Riley said his niece was being taken to a hospital so she could be treated and declared fit to fly home.
According to police, she unbuckled her seatbelt just minutes after take-off and opened one of the small Cessna's two doors.
She threw threw herself out after fighting off the pilot and fellow British passenger Ruth Johnson, who had grabbed onto her and lost their grip after becoming "exhausted" during the struggle, say police.
Mr Riley said his niece never suffered from mental illness, adding: "What happened, the family believe, was a tragic accident not a suicide and we are utterly heartbroken."
He said she had been hallucinating and she must have had a reaction to medication.
The plane's pilot said Ms Cutland had a headache when she boarded and stayed silent during the flight.
"But for the whole time Alana did not say a word - she just struggled to get away from us," Mahefa Tahina Rantoanina told the Sun.
"I have no idea why she opened the door but she did. She opened the door and she jumped. The door did not open itself."
Police photographs recreating Ms Cutland's final moments appear to show the pilot and the second passenger grasping hold of the victim's leg as she hangs out of the plane.
The force said Ms Cutland took off her seatbelt about 10 minutes into the flight, unlocked the right door and tried to get out.
That led to a desperate five-minute struggle in which the pilot and Ms Johnson tried to keep the teen on board.
Mr Riley said his niece met Ms Johnson during the trip.
Police believe Ms Cutland landed in an area populated by carnivorous fossas, cat-like mammals endemic to Madagascar.
The force said she was in regular contact with her parents and was making her way home via the island's main airport.
Family members said the second-year student "grasped every opportunity that was offered to her with enthusiasm and a sense of adventure" and was in Madagascar to complement her studies in natural sciences.
In a statement released through the Foreign Office, her family paid tribute saying: "Our daughter Alana was a bright, independent young woman, who was loved and admired by all those that knew her.
"Alana grasped every opportunity that was offered to her with enthusiasm and a sense of adventure, always seeking to extend her knowledge and experience in the best ways possible.
"She was particularly excited to be embarking on the next stage of her education, on an internship in Madagascar complementing her studies in natural sciences.
"We are heartbroken at the loss of our wonderful, beautiful daughter, who lit up every room she walked in to, and made people smile just by being there."
Her uncle said she wanted to wanted to work in wildlife and zoology after graduating from Cambridge.
