"The claim about the arrest of the AFP journalist is under investigation," the official IRNA news agency quoted Abbas Jaffari Doulatabadi as saying.
The prosecutor confirmed that a number of people were arrested on Wednesday as an annual commemoration of the November 4, 1979 storming of the US embassy by Islamist students was overshadowed by a counter-demonstration by critics of President Mahmoud Ahmadinejad's June re-election.
"Some people were arrested on November 4. The policy of the prosecutor's office is to release all those people against whom there are no accusations," he said.
"Some people have already been released."
Pouladi was detained on Wednesday morning by three security personnel, two in uniform and one in plainclothes, witnesses said.
He was riding pillion on a motorcycle when he was stopped.
The rider of the motorcycle said the security force officials confiscated the reporter's mobile phone and then escorted him away.
AFP has asked the Iranian authorities for the immediate release of Pouladi and is protesting his arrest and continued detention.
"We are worried for our journalist. We still don't know exactly where he is being held," AFP chairman Pierre Louette said on Thursday.
"We strongly protest his detention and we demand that he be released without delay," he added.
Iran's ministry of culture and Islamic guidance, which regulates the activities of the foreign press, told AFP on Thursday that Pouladi would not be released before the weekend.
"I am told that he definitely will not be released today or tomorrow. His case is being considered. Maybe he will be released on Saturday or Sunday," a ministry official said.
