State media say Saeed Mortazavi—an ally of President Mahmoud Ahmadinejad—was taken to Tehran's Evin prison late Monday night but gave no details.
Mortazavi was Tehran city prosecutor in 2009. At the time, he was responsible for Kahrizak prison, where at least three anti-government protesters were tortured to death. He now heads the country's social security fund.
Iran's reformists have openly criticized Mortazavi during his years in the judiciary. He was even dubbed "butcher of the press" for the closures of more than 120 newspapers and the imprisonment of dozens of journalists and political activists over the past 13 years.