Police say Gaia Pope suffered no injuries to suggest anyone else was involved in her death.
Following a post-mortem examination, officers said the 19-year-old's death was currently being treated as unexplained.
They said they were confident that a body found on Saturday afternoon was that of Gaia who went missing over a week ago.
Meanwhile, her twin sister has said she is "heartbroken" at the loss of her "beautiful twin".
Maya Pope-Sutherland wrote on Facebook: "Can't find any words right now. Gaia is my everything and I am heartbroken. I thank everyone who was involved in searching for my beautiful twin. Going to make her so proud."
The message appeared above a picture of her sister, with the message: "R.I.P Gaia".
The twins' cousin, Marienna Pope-Weidemann, posted a picture of herself with Gaia, 19, on Facebook with the words: "My beautiful baby girl, so sunny and kind but tough as f***.
"We hold you in our hearts forever. Know you are with Nan & Pops now but miss you beyond words. You will have justice. Fly on."
Detective Superintendent Paul Kessell said: "The post-mortem examination has not identified any injuries to suggest any other person was involved in her death. The cause of death is undetermined pending toxicology.
"The coroner is involved in the oversight of these examinations but at this time this remains an investigation into an unexplained death."
Gaia's body was found on land near Swanage, close to where her clothes were discovered in a field near cliffs on Thursday.
The teenager, who suffered from epilepsy, was last seen at about 4pm on 7 November in Manor Gardens, Swanage.
On Saturday, her elder sister Clara Pope said: "She is the absolute light of my life. So beautiful, so emotionally wise and intelligent and so passionate and artistic and creative... I will always, always, always be one of three."
Sheri Carr, a family friend of the Popes who organised the social media campaign to encourage volunteers to search for the teenager, spoke of her devastation of the loss.
"We are absolutely devastated, and unable to put into words our feeling of loss. We thank you for everything you have done," she wrote on Facebook.
"If there is one ray of light in this nightmare, it is the compassion, humanity and community spirit you've shown over the last 10 days."