The governments of the European Union's 25 members nations will be informally questioned about the allegations, EU spokesman Friso Roscam Abbing said.
"We have to find out what is exactly happening. We have all heard about this, then we have to see if it is confirmed."
Meanwhile, a senior administration official says President Bush's directive banning the torture of terror suspects applies to all prisoners — even if held in a secret prison reportedly set up by the CIA for its most important al Qaeda captives.
National Security Adviser Stephen Hadley would not confirm or deny the existence of a secret, Soviet-era compound in Eastern Europe that was described in a Washington Post account. The story said the facility was part of a covert prison system set up nearly four years ago that at various times has included sites in eight countries.
Roscam said such prisons could violate EU human rights laws and other European human rights conventions, and as the watchdog to ensure EU rules are properly adhered to the Commission would look into the issue. He cautioned that the EU head office as such could not take action against member states if they violated human rights.
"As far as the treatment of prisoners is concerned ... it is clear that all 25 member states having signed up to European Convention on Human Rights, and to the International Convention Against Torture, are due to respect and fully implement the obligations deriving from those treaties," Roscam Abbing told reporters.
Hadley said that "while we have to do what is necessary to defend the country against terrorist attacks and to win the war on terror, the president has been very clear that we're going to do that in a way that is consistent with our values."
"And that is why he's been very clear that the United States will not torture," Hadley said, responding to questions at a White House briefing. "The United States will conduct its activities in compliance with law and international obligations."
"It's just a bad system, because you don't get good information from interrogation in the first place. You get a lot of false leads. And, of course, this is just going to spawn terrorism at the end of the day," former CIA agent Robert Baer told the BBC. "Professional CIA officers know that this kind of torture and interrogation and indefinite detention doesn't get anyone anywhere, except create more terrorists."
"The fact that they are secret, assuming there are such sites, does not mean" torture would be tolerated, Hadley said.
"Some people say that the test of your principles (is) what you do when no one's looking. And the president has insisted that whether it is in the public or it is in the private, the same principles will apply and the same principles will be respected," Hadley said. "And to the extent people do not meet up, measure up to those principles, there will be accountability and responsibility."
Baer, author of the book "See No Evil" about the CIA efforts against terrorism, says what he calls the "bad system" was pushed from the top.
"It's the White House," Baer said. "People are leaving the CIA right and left. They're disgusted by the policies coming out of the White House. There are more people leaving since 9/11 since the entire history of the CIA."
Led by Vice President Dick Cheney, the Bush administration is floating a proposal that would allow the president to exempt covert agents outside the Defense Department from a Senate-approved ban on torturing detainees in U.S. custody or weakening the prohibition.