The Jakarta Globe said authorities are now investigating whether the kidnappers have links to terrorists.
Police said two men on motorcycles took Siti Nurjanah while she was buying food in front of her school on Jan. 17.
Jakarta Globe said kidnappers demanded $414,000 from her father, Nassar Farhat Ahmad Sungkar and his wife, and also sent threatening text messages, including a photo of the daughter handcuffed.
Police found the girl in a rented house in Bogor Saturday morning, and arrested one kidnapper, Fadlun Haryanto. The Jakarta Globe said the other man escaped.
"We found a plastic bag containing potassium and a [digital] book about jihad in their laptop," Jakarta Police Chief Inspector General Putut Eko Bayuseono said. "We're now coordinating with the National Police Anti-Terror Unit Densus 88 to check whether they have links to terrorism."
Fadlun was charged with child trafficking and kidnapping, and will face 15 years in prison.