A Polish investigation into secret CIA jails is being suppressed because it will embarrass the top echelon of the country’s government, lawyers of two men held illegally in one of the CIA’s ‘black sites’ in Poland tell media.

Reportedly, the results of this investigation could link some of Poland’s most senior politicians with illegal detention and torture, as well as impact negatively on the relationship between Poland and its key ally, the US, according to Reuters.

The news agency’s sources, including lawyers and human rights activists, reveal that the investigation was halted after the original investigators were taken off the case early last year.

The probe began in 2008 with prosecutors from the capital Warsaw, but in early 2012 the prosecutor-general transferred the investigation to the southern city of Krakow.

"The image is of a complete lack of action," Mikolaj Pietrzak, lawyer for Saudi national Abd al-Rahim al-Nashiri who says he was detained in a CIA jail on Polish soil, told Reuters. "The case is obviously, in my opinion, under political control … The most convenient thing politically is for the case to drag on," Pietrzak added.

Bartlomiej Jankowski, a lawyer for the second alleged ex-detainee, Abu Zubaydah, has confirmed this.

"I am not receiving any information [from prosecutors] about new documents, nor am I informed about any new hearings. This is something that worries me," Jankowski said.

CIA-run prison was discovered in a small remote village Stare Kiejkuty and was operational from December 2002 to the fall of 2003. It was used to transport suspected Al-Qaeda members outside the US territory to interrogate without having to adhere to US law.

Polish officials say the investigators are still in the midst of collecting evidence and the investigation is taking so long because US officials have not been responding to information requests.

In 2006, then-President George W. Bush revealed the US had CIA detention facilities overseas, but no details came out as to their exact locations.However, human rights groups named Afghanistan, Lithuania, Poland, Romania and Thailand as the most likely hosts.

The CIA’s black sites in Europe are rumored to have detained and tortured suspected terrorists, and to hold them in custody before being transported to the prison at Guantanamo Bay. The sites and the prisoners existed in legal limbo, with no oversight from citizens of the host countries. The CIA is believed to have operated with the knowledge and cooperation of the governments of those countries.

Poland is the second country to have opened a criminal investigation into the matter, after Lithuania (though that case has been closed).

Polish investigation is entering its fifth year, scheduled to end this month, but there are reports that the prosecutors may apply for an extension.

‘Investigation implicated senior levels of Polish government’

One of the main problems with the investigation is the fact that it affects top levels of Polish government, argues Polish Senator Jozef Pinior, who has pushed for a full investigation.

" [The government] are in a sandwich between opening this issue up and the pressure from the hard core of the Polish state, the secret service, the prosecutor's office, who say: 'Let's keep this secret'," Pinior told Reuters.

In response, Prime Minister Donald Tusk's office stated that the investigators are independent from external influence. "No executive body can influence the prosecutor's actions," it said in a statement.

Rumors about Poland hosting a CIA-run prison had circulated for years, though the country's authorities dismissed them as absurd.However, the UN and the Council of Europe had long claimed they had evidence of the site’s existence.

Also aware of the CIA program was Marek Dukaczewski, who was head of military intelligence when the alleged jail was in operation. He was the only one to acknowledge the CIA prison publicly in 2010.

Two prisoners from Guantanamo Bay, Abd al-Rahim al-Nashiri and Abu Zubaydah, claimed they were prisoners at this black site. Polish prosecutors have already given the two ‘victim status’.

Among other possible detainees are self-proclaimed 9/11 terrorist mastermind Khalid Sheikh Mohammed, perpetrator of the 2000 USS Cole bombing Abd al-Rahim al-Nashiri, and Palestinian terror suspect Abu Zubaydah.

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