Mehdi Karroubi, who was a candidate in Iran's June 12, 2009 presidential election and is one of the prominent figures challenging the validity of the election results, recently wrote to Hashemi Rafsanjani, the number two man in the Iranian regime, to inform him that young men and women arrested during the post-election protests were being raped while in prison. Karroubi also stated in the letter that he had appealed in this matter to senior regime figures, including judiciary head Ayatollah Shahroudi and Intelligence Minister Ejei (who has since been dismissed from his post), but had received no response. Karroubi called the rapes "a black stain that makes dictatorial regimes - including the Shah's - seem benign."
On August 9, 2009, the letter was published on the Saham News website, which is associated with Karroubi's party Etemad-e Melli. The website also reported that Karroubi had given Rafsanjani an ultimatum: if he did not deal with the matter within 10 days, Karroubi would make it public. The letter and accompanying report were removed from the site shortly thereafter, but were quoted by the Norouz News website.
The following are excerpts from the letter, as published by norooznews . 
"...The people who gave me this information hold sensitive positions in the regime... They say that all sorts of incidents are occurring in the prisons... Mr. Hashemi... Some of the detainees say that [certain] people [in the prisons] are raping girls who have been arrested, causing them vaginal tearing and injuries. They are also raping young boys, causing them depression and severe physical and emotional harm... so that [today, after their release] they hide in the corners of their homes.
"In light of the gravity of [these allegations], I expect you, as head of the Assembly of Experts, [to form] a committee to will investigate and deal with this matter objectively and transparently... so as to prevent thugs and hooligans from staining the reputation of the regime, of the Imam [Ayatollah Khomeini], of the Islamic Republic, and of the clerics who have been serving [society well] for thousands of years.
"I remind you that there are two copies of this letter: the one I sent to you and another that I am keeping."
Iranian Prosecutor-General Ayatollah Qorban Ali Dori Najafabadi has acknowledged that some detainees have been tortured in prison, saying: "Mistakes have led to some unfortunate and indefensible incidents, and those involved will have to be punished." This includes the incident at Kahrizak prison, where prisoners were killed, and which has [since] been closed on Khamenei's orders. 
 norooznews (Iran), August 9, 2009.
 Al-Sharq Al-Awsat (London), August 10, 2009. Hamid-Reza Katouzian, member of a Majlis committee formed to monitor the situation of the protest detainees, said that Iranian Police Chief Esmail Ahmadi-Moqaddam received daily reports about torture at this prison, contrary to his claims that he had known nothing and that the prisoners had died of a disease. Mehr (Iran), August 9, 2009.