A man arrested on suspicion of murdering the daughter ofTaggart actor John Michie is also being questioned on suspicion of supplying a Class A drug.
The body of Louella Eve Fletcher-Michie, 25, was discovered in a wooded area on the edge of the festival site at Lulworth Castle, Dorset, on Monday.
Officers were alerted to concerns for the welfare of Ms Michie, who was attending the event, just before 1am and her body was located following a search.
A 28-year-old man from London, who was known to Ms Michie, was arrested on suspicion of murder. He was later also arrested on suspicion of supplying a controlled Class A drug.
Dorset Police said a post-mortem examination was inconclusive and showed no clear signs of assault. Further tests, including a toxicology, will now be carried out.
These tests will establish whether there were any substances in Ms Michie's system, or any other suspicious circumstances.
Her father former Taggart, Holby City and Coronation Street actor John Michie, 66, said the family had lost their "angel" and described the death as "a tragic mistake, a tragic accident".
"She touched so many lives. She was so very positive, so bright, so out there. She had such energy. The tributes to her have been incredible," he told the newspaper.
In a statement, his agent said Mr Michie and wife Carol - a former Hot Gossip dancer - asked for privacy during the "traumatic time".
Mr Michie, who currently plays neurosurgeon Guy Self in BBC medical drama Holby City, has two other children, Daisy and Sam.
He played Karl Munro in Coronation Street from 2011 to 2013, having starred as Detective Inspector Robbie Ross in drama series Taggart from 1998 to 2010.
Ms Michie was born when her father was acting in Women Laughing in 1992, which was directed by actor and close family friend Richard Wilson.
Louella Fletcher-Michie. Source: Facebook
In a statement, Mr Wilson's agent said: "Richard Wilson, Louella's godfather, was very, very attached to her and does not feel able to comment at this present time."
Chriss and Tiffany Campbell-Welch, the directors of Tiffany Theatre College, paid tribute to former student Ms Michie.
"Louella was a very gifted student, a beautiful young lady with a sweet soul who was well loved by everyone, peers and mentors alike," they said.
"She had a wonderful ability to light up the room with her smile and make everyone feel happy."
Modelling agency The Eye Casting tweeted: "It is with profound sadness & shock that tonight we have heard of the death of our beautiful model Louella Michie.
"The thoughts of us all are with her sister Daisy & the rest of her family at this tragic time. We will be making no further statements."
On Monday, the organisers of Bestival said they were "devastated" by the death and were supporting police with the investigation.
The festival, organised by DJ Rob da Bank and his wife Josie, took place for the first time on the Lulworth Estate in Dorset this year. It was previously held on the Isle of Wight.
Acts including the XX, Dizzee Rascal, Rag 'n' Bone Man, Pet Shop Boys, Wiley and Laura Mvula performed at the four-day event.
A spokeswoman for Dorset Police declined to comment on which Class A drug the 28-year-old man had been arrested on suspicion of supplying.
Detective Chief Inspector Sarah Derbyshire, of Dorset Police, said: "Detectives are working tirelessly to investigate the full circumstances surrounding this tragic death.
"A post mortem examination took place that was inconclusive and therefore we need to undertake a number of other examinations before we can establish why she died.
"We continue to work with the festival organisers and our thoughts are with Louella's family at this extremely difficult time. We would ask that their privacy is respected."
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