Updated

Poland's prime minister said Saturday he has ordered an investigation into whether the CIA ran secret prisons for terror suspects in the country — an allegation the government repeatedly has denied.

Kazimierz Marcinkiewicz said a "detailed" probe would be conducted to "check if there is any proof that such an event took place in our country. It is necessary to finally close the issue because it could be dangerous to Poland."

Marcinkiewicz's spokesman, Konrad Ciesiolkiewicz, said he did not know who would carry out the investigation.

More than a half-dozen investigations are under way into whether European countries may have hosted secret U.S.-run prisons in which al-Qaida suspects were allegedly tortured, and whether European airports and airspace were used for alleged CIA flights transporting prisoners to countries where torture is practiced.

Secretary of State Condoleezza Rice has said the United States acts within the law and argued that Europeans are safer because of tough U.S. tactics. She refused to discuss intelligence operations or address questions about clandestine CIA detention centers.

Poland's outgoing President Aleksander Kwasniewski reiterated this week that "there are no such prisons or such prisoners on Polish territory." On Nov. 28, he said there "never have been" such jails in Poland.

But the Polish newspaper Gazeta Wyborcza reported Saturday that Gulfstream airplanes belonging to either the CIA or FBI landed at least five times at the Szczytno-Szymany airport in northeastern Poland since December 2002.

Reports last month that a CIA Boeing 737 landed at the same airport on Sept. 22, 2003, launched much of the speculation of how Poland has cooperated with the CIA.

Quoting unidentified former airport employees, the paper said Saturday the planes remained on the runway and did not refuel. Only border control officials and mini vans approached the aircrafts. One former employee said the vans were from nearby Kiejkuty, the site of a training school for Poland's intelligence services.

A former chief of Poland's intelligence agency, Zbibniew Siemietkowski, told the newspaper that Poland and American spies had cooperated "intensively" since the Sept. 11, 2001, attacks.

"It would be entirely normal if Americans landed in Mazury," Siemietkowski said, referring to the region where both the airport and intelligence school are located.

Marc Garlasco, a senior military analyst for the New York-based Human Rights Watch, said in remarks published Friday in Gazeta Wyborcza that Poland was the chief CIA detention site in Europe, part of a system of clandestine prisons for interrogating al-Qaida suspects.

The Council of Europe, the continent's top human rights watchdog, has also launched an investigation into the secret CIA prisons. EU leaders say any member states found to have been involved in such prisons could have their voting rights suspended.

Secret facilities and harsh interrogation methods would violate European human rights conventions.