Prosecutors for the first time questioned the woman allegedly held captive for 24 years by her father, and video of the interviews will be shown in court at the father's trial later this year, Austrian media reported Friday.
The Austria Press Agency, citing unidentified judicial sources, said 42-year-old Elisabeth Fritzl was interviewed Friday in a secret location.
Her father, 73-year-old Josef Fritzl, is expected to go on trial before the end of the year. Prosecutors allege he held his daughter in a windowless underground cell beneath his home and fathered seven children with her, tossing into a furnace the body of one of the babies after it died in infancy.
Investigators plan to resume questioning Elisabeth next week, APA said.
Public broadcaster ORF said Judge Andrea Humer, who will preside over Fritzl's trial, gave the go-ahead for Elisabeth to be questioned after medical experts pronounced her in good health.
Elisabeth, her children and her mother have been getting treatment and counseling at a psychiatric clinic guarded by police since Fritzl released his captives in late April after one of the children held underground became seriously ill and was hospitalized.
Authorities say Fritzl has confessed to fathering the seven children and disposing of the body of the infant who died, and they say DNA tests confirmed he is the surviving children's biological father.
Investigators say Fritzl brought three of the youngsters upstairs and raised them in the open with his wife, claiming Elisabeth had run away to join a cult and had later left the three on the family's doorstep in Amstetten, a town west of Vienna.
They say the other three children were confined in the cellar with Elisabeth - who was imprisoned shortly after she turned 18 - and never saw sunlight until they gained their freedom this spring.
ORF reported Friday that one of the children who lived upstairs - a 15-year-old girl - spent last weekend "incognito" at a youth fire brigade camp with 4,000 other youngsters and met up with some of her school friends for the first time in nearly three months.
Other family members also have made day trips outside under disguise, the Kurier newspaper reported.
Fritzl remains held in pretrial detention in St. Poelten, about 50 miles (80 kilometers) west of Vienna. He has not been charged yet.
Officials have said they will videotape any interviews with Fritzl's victims and show the tape in court to spare them the trauma of having to appear and testify.