Three people arrested on suspicion of murder after the death of Gaia Pope have been released from police investigation without any further action.
A post-mortem examination of the body found in the search for the missing 19-year-old "has not identified any injuries to suggest any other person was involved", Dorset police said in an update.
Police had arrested three people - two men aged 19 and 49 and a 71-year-old woman - on suspicion of murder.
Gaia suffered no injuries that could suggest someone else was involved in her death, police said.
Detective Superintendent Paul Kessell, of Dorset Police's Major Crime Investigation Team, said: "I appreciate our inquiries would have caused these individuals stress and anxiety, however we have an obligation in any missing person investigation to explore every possible line of inquiry.
"The public would expect Dorset Police to fully investigate the sudden disappearance of a teenage girl."
The body is yet to be formally identified, but police are confident it is that of Gaia.
Gaia, who suffered from severe epilepsy, was last seen in Swanage on 7 November and in the following days her family and volunteers scoured areas around the town in search of her.
The body was discovered on land to the south of the town at around 3pm on Saturday, close to where clothing identified as belonging to Gaia was found two days earlier.
Speaking just hours after the body was discovered, Clara Pope, Gaia's sister, tearfully told ITV News her sister had been "the light" of her life.