The Polish government said Monday that Poland's Prime Minister Donald Tusk has requested an investigation into allegations there were secret prisons in the country used by the CIA to hold and question terrorism suspects between 2001 and 2004. The request was confirmed Monday by government spokesman Jacek Filipowicz. Human rights groups have increasingly pressured the government to investigate 2005 allegations that Poland, a staunch US ally in Iraq, may have violated human rights by allowing the Bush administration to secretly hold and question terror suspects from Afghanistan on Polish territory. Two previous governments have vehemently denied such claims. A special EU commission investigated similar reports earlier. But the Helsinki Foundation for Human Rights, as well as Poland's ombudsman, Janusz Kochanowski, have pressed Tusk to investigate further. "The prime minister replied ... to say that he had asked the prosecutor general to hold a detailed investigation in order to clarify the matter," Filipowicz, the acting government spokesman, told The Associated Press.