Michael White, 46, has been held since July, and is the first known American to have been detained in Iran since Donald Trump became president. His family claims he traveled to Iran to visit his girlfriend, whom he apparently met online, and was detained, AP reported.
The Friday report quoted Gholamali Sadeqi, the prosecutor in the northeastern city of Mashhad, as saying that the case is still "under investigation."
He did not confirm reports that the man faces security charges. Under Iranian law, a private complaint would refer to allegations made by a citizen, not the state.
Trump has pursued a maximalist campaign against Tehran that includes pulling out of its nuclear deal with world powers.
Joanne White, the detainee's mother, issued a statement earlier this month calling on the Trump administration to secure his release.
Iran confirmed White’s arrest earlier this month after The New York Times reported that White was arrested in July while visiting his Iranian girlfriend.