Louella Michie, 25, was found dead at Bestival, and a 28-year-old has been held on suspicion of murder.
Dorset Police have no concluded intial post mortem results – revealing there was no obvious signs of assault.
Detectives are now also quizzing the arrested man over drug offences.
Her 60-year-old soap star dad John has hit back, claiming her death was a “tragic accident”.
The actor, who played Karl Munro, described her death as a “mistake” and denied it was murder.
John and his wife Carol reportedly sped down to the festival at Lulworth Castle in Dorset after receiving a panicked call and a message on WhatsApp.