It is thought Mr White was arrested in Mashhad is about 60 miles east of Tehran, Iran's capital (Picture: PA).
Iran has confirmed it is holding US Navy veteran Michael R. White at a prison in the country, making him the first American known to be detained under President Donald Trump's administration.
Mr White's detention adds new pressure to the rising tension between Iran and the US.
Relations between the nations have worsened under President Donald Trump who has pursued a campaign against Tehran that includes pulling out of its nuclear deal with world powers.
Although the circumstances of Mr White's imprisonment remain unclear, Iran in the past has used its detention of Westerners and dual nationals as leverage in negotiations.
The semi-official Tasnim news agency, believed to be close to the country's paramilitary Revolutionary Guard, reported the confirmation, citing foreign ministry spokesman Bahram Ghasemi.
"An American citizen was arrested in the city of Mashhad some time ago and his case was conveyed to the US administration on the first days" of his incarceration, Mr Ghasemi was quoted as saying.
The New York Times has quoted Mr White's mother saying she learned three weeks ago that her son is alive and being held at an Iranian prison.
His arrest was first reported by IranWire, an online news service run by one-time Iran detainee Maziar Bahari, which interviewed a former Iranian prisoner who said he met Mr White at Vakilabad Prison in Mashhad in October.
Mashhad is about 60 miles east of Tehran, Iran's capital.