Warsaw ? Poland’s prime minister said Saturday he has ordered an investigation into whether the CIA ran secret prisons for terrorist 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 U.S. acts within the law and argued that Europeans are safer because of tough U.S. tactics.

Poland’s outgoing President Aleksander Kwasniewski reiterated this week that “there are no such prisons or such prisoners on Polish territory.”

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.