STARE KIEJKUTY, Poland -- On an idyllic lake surrounded by woods and a double row of mesh-and-razor-wire fences about 100 miles north of Warsaw, there stands a secluded villa that the CIA once used to interrogate — and allegedly torture —top al Qaida suspects.

On the grounds of the Polish intelligence-training academy and nicknamed “Markus Wolf” for the former East German spy chief, it’s the focal point for a top-secret probe that Polish prosecutors have launched into how their government tolerated rampant violations of international and Polish law.

If former officials are brought to trial, or if the classified files in the prosecutors’ offices are made public, the result will be revelations about an American anti-terrorism operation whose details U.S. officials are fighting to keep secret.

Already the prosecutor has charged Zbigniew Siemiatkowski, Poland’s former interior minister and intelligence chief, with unlawful detention and corporal punishment for allowing the CIA to operate at Stare Kiejkuty from December 2002 to September 2003.

And the prosecutor’s office has given victim status in the case to two men the U.S. is holding indefinitely at Guantánamo: Abd al Rahim al Nashiri, a Saudi charged with orchestrating the 2000 bombing of the USS Cole off Yemen, and Zayn al Abdeen Mohammed Hussein, a Palestinian better known as Abu Zubaydah who was described by the Bush administration as a key catch in the war on terror. Nashiri faces a possible death sentence; Abu Zubaydah, who’s been held for 10 years, hasn’t been charged.

Their status as victims comes from claims that they were kidnapped by U.S. authorities, brought to Poland illegally, tortured, then spirited from Poland to other detention centers without the legally required extradition proceedings.

The villa cannot be seen from the main road or spotted on Google Earth maps. At the request of Polish authorities, its location has been blurred, the Polish newspaper Gazeta Wyborcza reported.

That’s what some parts of the Polish government would like to have happen to everything that took place here.

State prosecutors, however, seem motivated to bring the case to court. The Polish investigation is now in its fifth year, has twice been reassigned to new prosecutors and will run at least until mid-February, it was announced last week. It is, to date, the only criminal prosecution in the world related to the CIA’s so-called “black sites.”

The Obama administration has declined to investigate what happened at any of the sites, which included facilities in Thailand, Romania and Lithuania.

The prosecution is slow-going, but serious, according to Mikolaj Pietrzak, the Polish legal counsel for Guantánamo detainee Nashiri. The two prosecutors, Katarzyna Plonczyk and Janusz Sliwa, specialize in organized crime and counter-terrorism and are “very capable, very competent,” said Pietrzak, a former senior staffer of the Helsinki Foundation for Human Rights. His costs are borne by the Open Society Institute Justice Initiative, a U.S. foundation.

“The prosecutor is working very robustly. It is a very broad and thorough investigation — which doesn’t mean it’s effective,” he said in Warsaw. “Everything . . . could have been done much, much quicker.”

The prosecution has interviewed 62 witnesses and compiled 20 volumes of material, the Helsinki Foundation said. Pietrzak has yet to see all the documents that have been collected in Nashiri’s case. He’s been allowed to see unclassified files in Krakow, but he’s had only fleeting access to the classified documents — under a previous prosecutor. But what he’s seen convinces him that his client was terribly mistreated in the villa.