A man arrested in connection with the mystery death of Paula Newman last week is understood to be her boyfriend, Kane Boyce.
The 33-year-old was arrested on Tuesday after Miss Newman, of Beckenham, was taken ill at a house in Dunsfold Way, New Addington.
The 20-year-old died at Croydon University Hospital later that day, with a post-mortem examination establishing head injuries as the cause of death.
Mr Boyce was questioned by police for three days before being released on Friday.
Police believe Miss Newman's fatal injuries were inflicted after a fall from a black BMW 325 on November 11, between 8.45pm and 11.30pm, and are treating her death as suspicious.
They believe the fall was witnessed by at least one other person.
Paula Newman died last week
Detective Chief Inspector Diane Tudway, who is leading the investigation, said: "I believe this lady died as a result of the injuries sustained from falling from the car and that there may have been at least one other person in the BMW.
"I would urge that person, or anyone who witnessed the fall or has information that could help the enquiry to contact the incident room to help us piece together the events of that evening."
Miss Newman's brother Gary also appealed for information on Facebook, on which he launched a tribute page to his sister.
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