The European Commission (search) said Friday it would encourage governments in Eastern Europe to comment on allegations that the CIA (search) set up secret prisons in the region to interrogate Al Qaeda (search) suspects.

Polish authorities denied any knowledge of prisoner transfers, but -- in a piece of information that raises questions as much as it sheds light -- confirmed Friday that a plane carrying Americans touched down at a little-used airport on the very day a human rights group claims flight logs indicate a CIA aircraft landed there.

In Romania, officials gave The Associated Press computerized flight logs in an attempt to disprove claims of suspicious flights landing at an airport near a military base.

The broader allegations, first reported in the Washington Post, have also triggered a flurry of denials from other governments in the former Soviet bloc and prompted European Union (search) officials, the continent's top human rights organization and the international Red Cross (search) to say they would investigate. U.S. officials have refused to confirm or deny the claims.

"It is obvious we'll take the statements of those countries for true," said Friso Roscam Abbing, a European Union spokesman. "Only if we receive evidence which would prove the contrary will we decide what possible next steps to take in terms of contacting authorities."

Roscam Abbing said the European Commission -- the EU's executive office -- would seek statements from governments that have not denied the existence of secret prisons on their territories to comment on the issue "if only to get as much clarity and transparency as possible." Such prisons, European officials say, would violate the continent's human rights principles.

The commission said it would make an informal inquiry, requesting answers from all 25 member governments as well as EU candidates Romania, Bulgaria, Croatia and Turkey.

In Poland, an EU member, airport officials and border guards said that on Sept. 22, 2003, a Boeing passenger plane carrying seven people with U.S. passports touched down at midnight at Szczytno-Szymany airport, a former military base in the country's northeastern pine forests. Szczytno-Szymany is not an operating airport, but planes may land if arrangements are made in advance.

Border guards spokesman Maj. Roman Krzeminski said records show the plane took on five other people with U.S. passports who were waiting at the airport and whose documents said they came to Poland on business. He said the plane took off after about an hour on the ground.

Former airport director Mariola Przewloczka said border guards drove out to meet the plane on the runway instead of having the occupants enter the airport terminal. "After the plane landed, two vans drove out to meet it with border control officials," Przewloczka said.

She and other officials said they didn't know where the plane came from or where it went.

Several residents said they had not noticed any unusual flights.

"I didn't see anything, nothing," Marek Wyrzykowski, a farm worker who lives in a village next to the airport, told the AP. "Taliban? There's no Taliban here."

Human Rights Watch said Thursday it has evidence, based on tail numbers and flight logs of CIA aircraft from 2001 to 2004, that indicate the CIA transported suspects captured in Afghanistan to Poland and Romania.

Mark Garlasco, a senior military analyst with the New York-based organization, said the group matched the flight patterns with testimony from some of the hundreds of detainees in the war on terrorism who have been freed by the United States.

He said that in September 2003, a Boeing 737 flew from Washington to Kabul, Afghanistan, making stops in the Czech Republic and Uzbekistan. On Sept. 22 -- the same day Polish officials said a Boeing arrived -- he said the plane flew to Szczytno-Szymany Airport, then to Romania, Morocco and finally to the U.S. military base at Guantanamo Bay (search), Cuba.

In Romania, aviation officials and the military denied Human Rights Watch allegations that the Mihail Kogalniceanu Air Base may have been used by the CIA as a detention facility.

The United States used the Kogalniceanu base, near the Black Sea port of Constanta, to move troops and equipment during the wars in Afghanistan and Iraq. U.S. forces left the base in June 2003.

"When the Americans were here there were so many civilians working there, people would have found out about it," Dan Buciuman, the base commander, told the AP.

The head of the International Mihail Kogalniceanu airport, where planes carrying detainees are alleged to have landed, gave AP computerized flight logs for all landings from 2003 to 2005. There was no mention of the flights that have been reported in recent days as suspicious.

"It would be practically impossible for them to land here without a record," said airport director Cornel Balan. "These records cannot be erased or altered."

At the nearby air base, officers reacted with disbelief to the allegations that Kogalniceanu's facilities were used to keep secret CIA prisoners.

"It's incredible what is being said and to remove all doubts we have decided to open our doors, so that anyone can see that we have no detention facilities," said Lt. Cmdr. Adrian Vasile, a spokesman for the base.