WARSAW (Reuters) - The Polish prosecutor’s office is investigating allegations that there was a CIA prison in Poland where al Qaeda suspects were questioned and guards might have used methods close to torture, the prime minister’s top adviser said on Friday.

A guard shuts the gate to the airport in Szymany in northeastern Poland in this file 2005 picture. Human Rights Watch identified the airport as a potential site of alleged CIA prisons used to interrogate al Qaeda captives. Poland strongly denied it was hosting such facilities. REUTERS/FORUM/Tomasz Marek

Polish media reported earlier on Friday that a classified note written by the Polish secret service had proved the existence of a U.S. Central Intelligence Agency base in Poland.

“I am not familiar with such a note and I don’t think Prime Minister Donald Tusk is either,” Slawomir Nowak, who heads Tusk’s political office, said in an interview with Tok FM radio.

“But the premier asked the justice minister to clarify this matter and the country’s prosecutor’s office is investigating the potential existence of the CIA prison.”

The Washington Post reported for the first time in 2005, quoting unnamed CIA sources, that CIA prisons existed in Europe. A U.S. human rights group, Human Rights Watch, later said Poland and Romania hosted the prisons.

“There definitely was cooperation between Polish and American secret services,” a source close to the secret service told Reuters. “But whether there was torture at the base, hopefully we will learn about that soon.”

Foreign and local media speculated that the base was operational between 2002 and 2005, while Aleksander Kwasniewski was president and Poland was run by the leftist governments of Leszek Miller and Marek Belka and then a rightist administration under Kazimierz Marcinkiewicz.

DENIALS

All three have denied any knowledge of such a prison or base, as have many other senior officials including top secret service personnel. Tusk’s centre-right cabinet has also played down speculation about such a place.

“I hope this will not be confirmed,” Nowak said. “It would not only have serious consequences inside the country but would also take a very serious toll on the international scene.”

“This has to be investigated very carefully, without emotions.”

Defense Minister Bogdan Klich told a news conference on Friday he knew nothing about the case but that a final judgment should not be based on speculation.

Since 2005, separate reports by the Council of Europe, the European Parliament and the European Commission have concluded that CIA prisons did exist in Poland and Romania.

All Polish political parties have played down speculation about the existence of a CIA prison. Under Polish law, a Pole who was party to an agreement allowing the CIA to torture suspects could be sued in the regular courts or even in the State Tribunal, a special court for government officials.

“We demanded official information from the prime minister about the prisons in June, but we never got it,” said Dawid Szescilo of the Polish unit of the Helsinki Foundation for Human Rights.

“This is the third government that has banned (the release of) any information about the case, and public opinion should be given knowledge of all of this.”