The disappearance of 10-year-old Natascha Kampusch eight years ago sparked a huge hunt across Austria. A woman found near Vienna on Wednesday said she was the missing girl.
Natascha Kampusch's passport was found at the house where she was imprisoned.
The woman was held in a sealed garage at the house in Strasshof, north-eastern Vienna.
Police who searched the garage said it looked like a dungeon.
A hidden room measured four by three metres (yards), with a small entrance.
Inside were books, clothes and other supplies. The room was sound-proof and windowless.
Her kidnapper, 44-year-old Wolfgang Priklopil, died after throwing himself in front of a train.
Police are investigating whether Natascha Kampusch had been beaten or sexually abused by the kidnapper.